Systems, apparatuses, and methods for data speculation execution

ABSTRACT

Systems, methods, and apparatuses for data speculation execution (DSX) are described. In some embodiments, a hardware apparatus for performing DSX comprises a hardware decoder to decode an instruction, the instruction to include an opcode and an operand to store a portion of a fallback address, execution hardware to execute the decoded instruction to initiate a data speculative execution (DSX) region by activating DSX tracking hardware to track speculative memory accesses and detect ordering violations in the DSX region, and storing the fallback address.

FIELD OF INVENTION

The field of invention relates generally to computer processorarchitecture, and, more specifically, speculative execution.

BACKGROUND

Vectorizing loops containing possible cross-iteration dependences isnotoriously difficult. An exemplary loop of this type is:

for (i = 0; i < N; i++) {  A[i] = B[C[i]];  }

A naïve (and incorrect) vectorization of this loop would be:

for (i = 0; i < N; i + = SIMD_WIDTH) {  zmm0 = vmovdqu32 &C[i]  k1 =kxnor k1, k1  zmm1 = vgatherdd B, zmm0, k1  vmovdqu &A[i], zmm1 }

However, if the compiler generating the vectorized version of the loophas no a priori knowledge about the addresses or alignment of A, B, andC, then the above vectorization is unsafe.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings, in which likereferences indicate similar elements and in which:

FIG. 1 is an embodiment of an exemplary block diagram of a processorcore capable of executing data speculation extension (DSX) in hardware;

FIG. 2 illustrates an example of speculative instruction executionaccording to an embodiment;

FIG. 3 illustrates a detailed embodiment of DSX tracking hardwareillustrates a detailed embodiment of DSX tracking hardware;

FIG. 4 illustrates an exemplary method of DSX mis-speculation detectionperformed by DSX tracking hardware;

FIGS. 5(A)-(B) illustrate an exemplary method of DSX mis-speculationdetection performed by DSX tracking hardware;

FIG. 6 illustrates an embodiment of an execution of an instruction forbeginning DSX;

FIG. 7 illustrates some exemplary embodiments of a YBEGIN instructionformat;

FIG. 8 illustrates a detailed embodiment of an execution of aninstruction such as a YBEGIN instruction;

FIG. 9 illustrates an example of pseudo-code showing the execution of aninstruction such as a YBEGIN instruction;

FIG. 10 illustrates an embodiment of an execution of an instruction forbeginning DSX;

FIG. 11 illustrates some exemplary embodiments of a YBEGIN WITH STRIDEinstruction format;

FIG. 12 illustrates a detailed embodiment of an execution of aninstruction such as a YBEGIN WITH STRIDE instruction;

FIG. 13 illustrates an embodiment of an execution of an instruction forcontinuing a DSX without ending it;

FIG. 14 illustrates some exemplary embodiments of a YCONTINUEinstruction format;

FIG. 15 illustrates a detailed embodiment of an execution of aninstruction such as a YCONTINUE instruction;

FIG. 16 illustrates an example of pseudo-code showing the execution ofan instruction such as a YCONTINUE instruction;

FIG. 17 illustrates an embodiment of an execution of an instruction foraborting a DSX;

FIG. 18 illustrates some exemplary embodiments of a YABORT instructionformat;

FIG. 19 illustrates a detailed embodiment of an execution of aninstruction such as a YABORT instruction;

FIG. 20 illustrates an example of pseudo-code showing the execution ofan instruction such as a YABORT instruction;

FIG. 21 illustrates an embodiment of an execution of an instruction fortesting the status of DSX;

FIG. 22 illustrates some exemplary embodiments of a YTEST instructionformat;

FIG. 23 illustrates an example of pseudo-code showing the execution ofan instruction such as a YTEST instruction;

FIG. 24 illustrates an embodiment of an execution of an instruction forending a DSX;

FIG. 25 illustrates some exemplary embodiments of a YEND instructionformat;

FIG. 26 illustrates a detailed embodiment of an execution of aninstruction such as a YEND instruction;

FIG. 27 illustrates an example of pseudo-code showing the execution ofan instruction such as a YEND instruction;

FIGS. 28A-28B are block diagrams illustrating a generic vector friendlyinstruction format and instruction templates thereof according toembodiments of the invention;

FIGS. 29A-D shows a specific vector friendly instruction format 2900that is specific in the sense that it specifies the location, size,interpretation, and order of the fields, as well as values for some ofthose fields.

FIG. 30 is a block diagram of a register architecture according to oneembodiment of the invention;

FIG. 31A is a block diagram illustrating both an exemplary in-orderpipeline and an exemplary register renaming, out-of-orderissue/execution pipeline according to embodiments of the invention;

FIGS. 32A-B illustrate a block diagram of a more specific exemplaryin-order core architecture, which core would be one of several logicblocks (including other cores of the same type and/or different types)in a chip;

FIG. 33 is a block diagram of a processor that may have more than onecore, may have an integrated memory controller, and may have integratedgraphics according to embodiments of the invention;

FIG. 34 shows a block diagram of a system in accordance with anembodiment of the present invention;

FIG. 35 shows a block diagram of a first more specific exemplary systemin accordance with an embodiment of the present invention;

FIG. 36 shows block diagram of a second more specific exemplary systemin accordance with an embodiment of the present invention;

FIG. 37 shows a block diagram of a SoC in accordance with an embodimentof the present invention;

FIG. 38 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knowncircuits, structures and techniques have not been shown in detail inorder not to obscure the understanding of this description.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

Throughout this description a technique of speculative executionreferred to as data speculation extension (DSX) is detailed. Included inthis description is DSX hardware and new instructions that support DSX.

DSX is similar in nature to restricted transactional memory (RTM)implementations, but simpler. For example, a DSX region does not requirean implied fence. Rather, normal load/store ordering rules aremaintained. Moreover, the DSX region does not set any configuration inthe processor forcing atomic behavior for loads, whereas in RTM, loadsand stores of a transaction are treated atomically (committed uponcompletion of the transaction). Additionally, loads are not buffered asthey are in RTM. However, stores are buffered and committed at once whenspeculation is no longer needed. These stores may be buffered indedicated speculative execution storage or in shared registers or memorylocations depending upon the embodiment. In some embodiments,speculative vectorization only happens on a single thread which meansthere is no need to protect against interferences from other threads.

In the previously detailed vectorized loop, there would need to bedynamic checks for safety. For example, an assurance that writes to A ina given vector iteration do not overlap elements in B or C that, in thescalar loop, are read in later iterations. Embodiments below detailhandling vectorization cases through the use of speculation. Aspeculative version indicates that each loop iteration should beexecuted speculatively (e.g., using instructions detailed below), andthat hardware should help to perform the address checks. Instead ofrelying on the hardware to be solely responsible for the address checks(which requires very expensive hardware), the detailed approach usessoftware to provide information to assist the hardware, enabling a muchcheaper hardware solution without impacting execution time or placingtoo much burden on the programmer or compiler.

Unfortunately, with vectorization there may be an ordering violation.Looking back at the scalar loop example detailed above:

for (i = 0; i < N; i++) {  A[i] = B[C[i]]; }

During the first four iterations of this loop, the following memoryoperations will occur in the following order:

Read C[0] Read B[C[0]] Write A[0] Read C[1] Read B[C[1]] Write A[1] ReadC[2] Read B[C[2]] Write A[2] Read C[3] Read B[C[3]] Write A[3]

The distance (in number of operations) between accesses to the samearray is three and it is also the number of speculative memoryinstructions in the loop once it is vectorized (made into SIMD). Thatdistance is called a “stride.” It is also the number of memoryinstructions in the loop that will have address checks performed on themonce the loop is vectorized. In some embodiments, this stride isconveyed to the address tracking hardware via a special instruction atthe start of the loop (detailed below). In some embodiments, thatinstruction also clears the address tracking hardware.

Detailed herein are new instructions (DSX memory instructions) used inDSX in cases such as vectorized loop execution. Each DSX memoryinstruction (such as loads, stores, gathers, and scatters) includes anoperand to be used during DSX that indicates a position within the DSXexecution (e.g., a position in a loop being executed). In someembodiments, the operand is an immediate (e.g., an 8-bit immediate) witha numerical value of encoded order in the immediate. In otherembodiments, the operand is a register or memory location storing anumerical value of encoded order.

Additionally, in some embodiments these instructions have a differentopcode than their normal counterpart. These instructions may be scalaror superscalar (e.g., SIMD or MIMD). Examples of some of theseinstructions are found below where the mneumonic of the opcode includesan “S” (which is underlined below) to indicate that it is a speculativeversion and the imm8 is an immediate operand that is used to indicate aposition of execution (e.g., a position in a loop being executed):

VMOVSDQA32 zmm1 {k1}{z}, mV, imm8//speculative SIMD loadVMOVS xmm1, m32, imm8//speculative scalar loadVSCATTERSDPS vm32z {k1}, zmm1, imm8//speculative scatter

Of course, other instructions may also utilize the detailed operand andopcode mneumonic (and underlying opcode) change such as logical (AND,OR, XOR, etc.) and data manipulation (add, subtract, etc.) instructions.

In a vectorized version (assuming a SIMD width of four packed dataelements) of the above scalar example, the order of memory operationsis:

Read C[0], C[1], C[2], C[3] Read B[C[0]], B[C[1]], B[C[2]], B[C[3]]Write A[0], A[1], A[2], A[3]

This order may lead to an incorrect execution if, for example, B[C[1]]overlaps with A[0]. In the original scalar order, the read of B[C[1]]happens after the write to A[0], but in the vectorized execution ithappens before.

Using speculative memory instructions for the operations in the loopthat might lead to incorrect execution helps deal with this problem. Aswill be detailed, each speculative memory instruction notifies a DSXtracking hardware (detailed below) of its position within the loop body:

for (i = 0; i < N; i += SIMD_WIDTH) { zmm0 = vmovsdqu32 &C[i], 0 //tells address tracker this is instruction 0 k1 = kxnor k1, k1 zmm1 =vgathersdd B, zmm0, k1, 1 // tell address tracker this is instruction 1vmovsdqu &A[i], zmm1, 2 // tell address tracker this is instruction 2 }

The loop position information provided by each speculative memoryoperation can be combined with the stride to reconstruct the scalarmemory operation. As speculative memory instructions execute, anidentifier (id) is computed by the DSX hardware tracker for each element(id=sequence number+stride*element number within the SIMD operation).The hardware tracker uses the sequence number, the calculated id, andthe address and size of each packed data element to determine if therewas an ordering violation (i.e., if the element overlaps with anotherand was read or written out of order).

Unrolling the individual memory operations that comprise each vectormemory instruction, accumulating the stride for each unrolling, andassigning the resulting numbers as “ids”, results in:

Read C[0]//id=0 Read C[1]//id=3 Read C[2]//id=6 Read C[3]//id=9 ReadB[C[0]]//id=1 Read B[C[1]]//id=4 Read B[C[2]]//id=7 Read B[C[3]]//id=10Write A[0]//id=2 Write A[1]//id=5 Write A[2]//id=8 Write A[3]//id=11

Sorting the above individual memory operations by id will reconstructthe original scalar memory ordering.

FIG. 1 is an embodiment of an exemplary block diagram of a processorcore capable of executing data speculation extension (DSX) in hardware.

The processor core 106 may include a fetch unit 102 to fetchinstructions for execution by the core 106. For example, theinstructions may be fetched from an L1 cache or memory. Core 106 mayalso include a decode unit 104 to decode the fetched instructionincluding those detailed below. For instance, the decode unit 104 maydecode the fetched instruction into a plurality of micro-operations(micro-ops).

Additionally, the core 106 may include a schedule unit 107. Scheduleunit 107 may perform various operations associated with storing decodedinstructions (e.g., received from the decode unit 104) until theinstructions are ready for dispatch, e.g., until all source values fromoperands of a decoded instruction become available. In one embodiment,schedule unit 107 may schedule and/or issue (or dispatch) decodedinstructions to one or more execution units 108 for execution. Executionunit 108 may include a memory execution unit, an integer execution unit,a floating-point execution unit, or other execution units. A retirementunit 110 may retire executed instructions after they are committed. Inan embodiment, retirement of the executed instructions may result inprocessor state being committed from the execution of the instructions,physical registers used by the instructions being de-allocated, etc.

A memory order buffer (MOB) 118 may include a load buffer, a storebuffer and logic to store pending memory operations that have not loadedor written back to a main memory. In some embodiments, the MOB 118 orcircuitry similar to it, stores speculative stores (writes) of a DSXregion. In various embodiments, a core may include a local cache, e.g.,a private cache such as cache 116 that may include one or more cachelines 124 (e.g., cache lines 0 through W and that is managed by cachecircuitry 139. In an embodiment, each line of cache 116 may include aDSX read bit 126 and/or a DSX write bit 128 for each thread executing oncore 106. Bits 126 and 128 may be set or cleared to indicate (loadand/or store) access to the corresponding cache line by a DSX memoryaccess request. Note that while in the embodiment of FIG. 1 each cacheline 124 is shown as having a respective bit 126 and 128, otherconfigurations are possible. For example, a DSX read bit 126 (or DSXwrite bit 128) may correspond to a select portion of the cache 116, suchas a cache block or other portion of the cache 116. Also, the bits 126and/or 128 may be stored in locations other than the cache 116.

To aid in executing DSX operations, core 106 may include a DSX nestcounter 130 to store a value corresponding to the number of DSX startsthat have been encountered with no matching DSX end. Counter 130 may beimplemented as any type of a storage device such as a hardware registeror a variable stored in a memory (e.g., system memory or cache 116).Core 106 may also include a DSX nest counter circuitry 132 to update thevalue stored in the counter 130. Core 106 may include a DSX checkpointing circuitry 134 to check point (or store) the state of variouscomponents of the core 106 and a DSX restoration circuitry 136 torestore the state of various components of the core 106, e.g., on abortof a given DSX, using a fallback address that either it stores or isstored in another location such as a register 140. Additionally, core106 may include one or more additional registers 140 that correspond tovarious DSX memory access requests, such as a DSX status and controlregister (DSXSR) to store an indication of if a DSX is active, a DSXinstruction pointer (DSXXIP) (e.g., that may be an instruction pointerto an instruction at the beginning (or immediately preceding) of thecorresponding DSX), and/or a DSX stack pointer (DSXSP) (e.g., that maybe a stack pointer to the head of a stack that stores various states ofone or more components of core 106). These registers may also be MSRs150.

DSX address tracking hardware 152 (sometimes simply called DSX trackinghardware) tracks speculative memory accesses and detects orderingviolations in a DSX. In particular, this tracking hardware 152 includesan address tracker that takes in information to reconstruct and thenenforce the original scalar memory order. Typically, the inputs are thenumber of speculative memory instructions in the loop body that need tobe tracked, and some information for each of those instructions such as:(1) a sequence number, (2) the addresses the instruction accesses, and(3) whether the instruction incurs reads or writes to memory. If twospeculative memory instructions access overlapping parts of memory, thehardware tracker 152 uses this information to determine if the originalscalar order of the memory operations has been changed. If so, and ifeither operation is a write, the hardware triggers a mis-speculation.While FIG. 1 illustrates DSX tracking hardware 152 on its own, in someembodiments this hardware is a part of other core components.

FIG. 2 illustrates an example of speculative instruction executionaccording to an embodiment. At 201, the speculative instruction isfetched. For example, a speculative memory instruction such as thosedetailed above is fetched. In some embodiments, this instructionincludes an opcode indicating its speculative nature and an operand toindicate an ordering in a DSX. The ordering operand may be an immediatevalue or a register/memory location.

The fetched speculative instruction is decoded at 203.

A determination of if the decoded speculative instruction is a part of aDSX is made at 205. For example, is a DSX indicated in the DSX statusand control register (DSXSR) detailed above? When a DSX is not active,the instruction either becomes a no operation (nop) or is executed as anormal, non-speculative instruction at 207 according to an embodiment.

When a DSX is active, the speculative instruction is speculativelyexecuted (e.g., not committed) and the DSX tracking hardware is updatedat 209.

FIG. 3 illustrates a detailed embodiment of DSX address trackinghardware. This hardware tracks speculative memory instance. Typically,an element (e.g., SIMD element) analyzed by DSX tracking hardware isbroken into portions called chunks which are no more than “B” bytes insize.

Shifting circuitry 301 shifts an address (such as a starting address) ofa chunk. In most embodiments, the shifting circuitry 301 performs aright shift. Typically, the right shift is by log₂B. The shifted addressis subjected to a hash function performed by hash function unitcircuitry 303.

The output of the hash function is an index to a hash table 305. Asillustrated, the hash table 305 includes a plurality of buckets 307. Insome embodiments, the hash table 305 is a Bloom filter. The hash table305 is used to detect mis-speculation, and to record the addresses,access type, sequence numbers, and id numbers of speculatively accesseddata. The hash table 305 contains N “sets” with each set containing Mentries 309. Each entry 309 holds a valid bit, sequence number, idnumber, and access type for an element of a previously executedspeculative memory instruction. In some embodiments, each entry 309 alsocontains a corresponding address (shown as a dashed box in the figure).Upon a DSX initiating instruction (e.g., YBEGIN and variants detailedbelow), all valid bits are cleared, and a “speculation active” flag isset, and on an instruction ending the DSX, the speculation active flagis cleared.

Conflict check circuitry 311 checks for a conflict per entry 309 againstthe element (or chunk thereof) under test 315. In some embodiments,there is a conflict when the entry 309 is valid and at least one of: i)the access type in the entry 309 is write or ii) the access type undertest is write, along with one of: i) the sequence number in the entry309 being less than the sequence number of the element under test 315,and the id number in the entry 309 being greater than the id number ofthe element under test 315 or ii) the sequence number in the entry 309being greater than the sequence number of the element under test 315,and the id number in the entry 309 being less than the id number of theelement under test 315.

In other words, a conflict exists when:

(Entry is valid) AND ((access type in entry==write) OR (access typeunder test=write)) AND (((Seq # in entry <Seq # under test) AND (id # inentry >id # under test)) OR ((Seq # in entry >Seq # under test) AND (id# in entry <id # under test)))

Note in most embodiments there is not a test for address overlap. Thisoverlap is implied from hitting the entry in the hash table. A hit mayoccur where there is no address overlap, due to aliasing from the hashfunction and/or from the check being too coarse-grained (i.e., B beingtoo large). However, there will be a hit when there is address overlap.So correctness is guaranteed, but there may be false positives (i.e.,the hardware may detect mis-speculation where there is none). In anembodiment, the chunk address is stored in each entry 309, and anadditional condition for testing for mis-speculation is applied (i.e.,this is logically ANDed with the above condition) where the address inentry 309 equals the address in the element under test 315).

An OR gate 313 (or equivalent) logically ORs the results of the conflictchecks. When the result of the ORing is a 1, then a mis-speculation haslikely occurred and the OR gate 313 indicates that with its output.

The total storage of this embodiment is M*N entries. That means it maytrack up to M*N speculatively accessed data elements. In practice,however, loops are likely to have more accesses to some of the N setsthan to others. If space in any set runs out, then in some embodiments amis-speculation is triggered to guarantee correctness. Increasing Malleviates this problem, but may force more copies of the conflictchecking hardware to exist. To perform all M conflict checkssimultaneously (as is done in some embodiments), there are M copies ofthe conflict checking logic.

Choosing the B, N, M, and hash function in a certain way, allows for thestructure to be organized in a very similar manner as the L1 data cache.In particular, let B be the cache line size, N be the number of sets inthe L1 data cache, M be the associativity of the L1 data cache, and letthe hash function be the least significant bits of the address (afterthe right shift). This structure will have the same number of entriesand organization as the L1 data cache, which may simplify itsimplementation.

Finally, note that an alternative embodiment uses separate Bloom filtersfor reads and writes, to avoid having to store the access typeinformation, and to avoid having to check the access type during theconflict checks. Instead, for reads, the embodiment performs conflictchecks against only the “write” filter, and if there is nomis-speculation, inserts the element into the “read” filter. Similarly,for writes, the embodiment performs conflict checks against both the“read” and “write” filters, and if there is no mis-speculation, insertsthe element into the “write” filter.

FIG. 4 illustrates an exemplary method of DSX mis-speculation detectionperformed by DSX tracking hardware. At 401, DSX is started or a previousspeculative iteration is committed. For example, a YBEGIN instruction isexecuted. The execution of this instruction clears the valid bits in theentries 309 and sets a speculation active flag (if not already set) in astatus register (such as the DSX status register detailed earlier). Aspeculative memory instruction is executed after the DSX is started andprovides data elements under test.

At 403, the data element under test from the speculative memoryinstruction is broken into chunks of no more than B bytes. The hashtable is accessed at a granularity of B bytes (i.e., the low bits of anaddress are discarded). If elements are large enough and/or are notaligned, they may cross a B byte boundary and, if so, the element isbroken into multiple chunks.

Per chunk, the following (405-421) are performed. The start address ofthe chunk is right shifted by log₂B. The shifted address is hashed at407 to generate an index value.

Using the index value, a look-up of a corresponding set of the hashtable is made at 409 and all entries of the set are read out at 411.

For each read out entry, a conflict check against the element under test(such as that described above) is performed at 413. An ORing of all ofthe conflict checks is performed at 415. If any check indicates aconflict at 417 (such that the OR is a 1), then an indication ofmis-speculation is made at 419. The DSX is typically aborted at thistime. If there is no mis-speculation, then at 421 an invalid entry inthe set is found and filled with the information for the element undertest and marked valid. If no invalid entries exist, a mis-speculation istriggered.

FIGS. 5(A)-(B) illustrate an exemplary method of DSX mis-speculationdetection performed by DSX tracking hardware. At 501, DSX is started ora previous speculative iteration is committed. For example, a YBEGINinstruction is executed.

The execution of this instruction resets the tracking hardware byclearing the valid bits in the entries 309 and sets a speculation activeflag (if not already set) in a status register (such as the DSX statusregister detailed earlier) at 503.

At 505, a speculative memory instruction is executed. Examples of theseinstructions are detailed above. A counter which is an element numberunder test (e) from the speculative instruction is set to zero at 507and an id is calculated (id=sequence number+stride*e) at 509.

A determination of if any previous write overlaps with the counter valuee is made at 511. This acts as a dependency check against previousstores (writes). For any overlapping writes, at 513 a conflict check isperformed. In some embodiments, this conflict check is looking to seeif: i) the sequence number in the entry 309 is less than the sequencenumber of the element under test 315, and the id number in the entry 309is greater than the id number of the element under test 315, or ii) thesequence number in the entry 309 is greater than the sequence number ofthe element under test 315, and the id number in the entry 309 is lessthan the id number of the element under test 315.

If there is a conflict, then a mis-speculation is triggered at 515. Ifnot, or if there were not previous writes that overlapped, then adetermination of if the speculative memory instruction is a write ismade at 517.

If yes, then a determination of any previous read overlaps with thecounter value e is made at 519. This acts as a dependency check againstprevious loads (reads). For any overlapping reads, at 521 a conflictcheck is performed. In some embodiments, this conflict check is lookingto see if i) the sequence number in the entry 309 being less than thesequence number of the element under test 315, and the id number in theentry 309 being greater than the id number of the element under test315, or ii) the sequence number in the entry 309 being greater than thesequence number of the element under test 315, and the id number in theentry 309 being less than the id number of the element under test 315.

If there is a conflict, then a mis-speculation is triggered at 523. Ifnot, or if there were not previous reads that overlapped, then thecounter e is incremented at 525.

A determination of if the counter e is equal to the number of elementsin the speculative memory instruction is made at 526. In other words,have all elements been evaluated? If no, then another id is calculatedat 509. If yes, then the hardware waits for another instruction toexecute at 527. When the next instruction is another speculative memoryinstruction, then the counter is reset at 507. When the next instructionis YBEGIN, then the hardware is reset, etc. at 503. When the nextinstruction is YEND, then the DSX is disabled at 529.

YBEGIN Instruction

FIG. 6 illustrates an embodiment of an execution of an instruction forbeginning DSX. As will be detailed herein, this instruction is referredto as “YBEGIN” and is used to signal the beginning of a DSX region. Ofcourse, the instruction may be referred to by another name. In someembodiments, this execution is performed on one more hardware cores of ahardware device such as a central processing unit (CPU), graphicsprocessing unit (GPU), accelerated processing unit (APU), digital signalprocessor (DSP), etc. In other embodiments, the execution of theinstruction is an emulation.

At 601, a YBEGIN instruction is received/fetched. For example, theinstruction is fetched from memory into an instruction cache or fetchedfrom an instruction cache. The fetched instruction may take one ofseveral forms as detailed below.

FIG. 7 illustrates some exemplary embodiments of a YBEGIN instructionformat. In an embodiment, the YBEGIN instruction includes an opcode(YBEGIN) and a single operand to provide a displacement for a fallbackaddress which is where program execution should go to handle amis-speculation as shown in 701. In essence, the displacement value is aportion of the fallback address. In some embodiments, this displacementvalue is provided as an immediate operand. In other embodiments, thisdisplacement value is stored in a register or memory location operand.Depending upon the YBEGIN implementation implicit operands for a DSXstatus register, a nesting count register, and/or a RTM status registerare used. As detailed earlier, the DSX status register may be adedicated register, a flag in a register not dedicated to DSX status(such as an overall status register like a flag register), etc.

In another embodiment, the YBEGIN instruction includes not only anopcode and displacement operand, but also an explicit operand for DSXstatus such as a DSX status register as shown in 703. Depending upon theYBEGIN implementation implicit operands for a nesting count registerand/or a RTM status register are used. As detailed earlier, the DSXstatus register may be a dedicated register, a flag in a register notdedicated to DSX status (such as an overall status register like a flagregister), etc.

In another embodiment, the YBEGIN instruction includes not only anopcode and displacement operand, but also an explicit operand for DSXnesting count such as a DSX nest count register as shown in 705. Asdetailed earlier, the DSX nest count may be a dedicated register, a flagin a register not dedicated to DSX nest count (such as an overall statusregister). Depending upon the YBEGIN implementation implicit operandsfor a DSX status register and/or a RTM status register are used. Asdetailed earlier, the DSX status register may be a dedicated register, aflag in a register not dedicated to DSX status (such as an overallstatus register like a flag register), etc.

In another embodiment, the YBEGIN instruction includes not only anopcode and displacement operand, but also explicit operands for DSXstatus such as a DSX status register and DSX nesting count such as a DSXnest count register as shown in 707. As detailed earlier, the DSX statusregister may be a dedicated register, a flag in a register not dedicatedto DSX status (such as an overall status register like a flag register,etc.), and the DSX nest count may be a dedicated register, a flag in aregister not dedicated to DSX nest count (such as an overall statusregister. Depending upon the YBEGIN implementation an implicit operandfor a RTM status register is used. As detailed earlier, the DSX statusregister may be a dedicated register, a flag in a register not dedicatedto DSX status (such as an overall status register like a flag register),etc.

In another embodiment, the YBEGIN instruction includes not only anopcode and displacement operand, but explicit operands for DSX statussuch as a DSX status register, DSX nesting count such as a DSX nestcount register, and RTM status as shown in 709. As detailed earlier, theDSX status register may be a dedicated register, a flag in a registernot dedicated to DSX status (such as an overall status register like aflag register, etc., and the DSX nest count may be a dedicated register,a flag in a register not dedicated to DSX nest count (such as an overallstatus register).

Of course other variants of YBEGIN are possible. For example, instead ofproviding a displacement value, the instruction includes the fallbackaddress itself in either an immediate, register, or memory location.

Turning back to FIG. 6, the fetched/received YBEGIN instruction isdecoded at 603. In some embodiments, the instruction is decoded by ahardware decoder such as those detailed later. In some embodiments, theinstruction is decoded into micro-operations (micro-ops). For example,some CISC based machines typically use micro-operations that are derivedfrom a macro-instruction. In other embodiments, the decoding is a partof a software routine such as a just-in-time compilation.

At 605, any operand associated with the decoded instruction isretrieved. For example, the data from one or more of a DSX register, DSXnest count register, and/or a RTM status register are retrieved.

The decoded YBEGIN instruction is executed at 607. In embodiments wherethe instruction is decoded into micro-ops, these micro-ops are executed.The execution of the decoded instruction causes the hardware to do oneor more of the following acts to be performed: 1) determine that an RTMtransaction is active and continue that transaction; 2) calculate afallback address using the displacement value added to the instructionpointer of the YBEGIN instruction; 3) increment the DSX nesting count;4) abort; 5) set DSX status to active; and/or 6) reset DSX trackinghardware.

Typically, upon an instance of an YBEGIN instruction, if there is not anactive RTM transaction, then the DSX status is set to active, the DSXnest count is incremented (if the count is less than a max), the DSXtracking hardware is reset (for example, as detailed above), and afallback address is calculated using the displacement value to start aDSX region. As detailed earlier, a status for a DSX is typically storedin an accessible location such as a register such as the DSX status andcontrol register (DSXSR) discussed above with respect to FIG. 1.However, other means such as a DSX status flag in a non-dedicatedcontrol/status register (such as a FLAGS register) may be utilized.Resetting of the DSX tracking hardware was also previously described. Asdetailed earlier, a status for a DSX is typically stored in anaccessible location such as a register such as the DSX status andcontrol register (DSXSR) discussed above with respect to FIG. 1.However, other means such as a DSX status flag in a non-dedicatedcontrol/status register (such as a FLAGS register) may be utilized. Thisregister may be checked by the hardware of the core to determine if aDSX was indeed taking place.

If there was some reason that the DSX cannot start, then one or more ofthe other potential actions takes place. For example, in someembodiments of processors that support RTM, if a RTM transaction wasactive then there should not have been a DSX active in the first placeand the RTM is pursued. If there is something wrong with the set up ofthe DSX in the first place (nest count not correct), then an abort willtake place. Additionally, in some embodiments, if there was no DSX thena fault is generated and no operations (a NOP) are performed. Regardlessof which act is performed, in most embodiments after that act the DSXstate is reset (if it was set) to indicate that there is no pending DSX.

FIG. 8 illustrates a detailed embodiment of an execution of aninstruction such as a YBEGIN instruction. For example, in someembodiments this flow is box 607 of FIG. 6. In some embodiments, thisexecution is performed on one more hardware cores of a hardware devicesuch as a central processing unit (CPU), graphics processing unit (GPU),accelerated processing unit (APU), digital signal processor (DSP), etc.In other embodiments, the execution of the instruction is an emulation.

In some embodiments, for example in a processor that supports RTMtransactions, a determination of if a RTM transaction is occurring ismade at 801. For example, in some embodiments of processors that supportRTM, if a RTM transaction was active then there should not have been aDSX active in the first place. In this instance, something went wrong inthe RTM transaction and its ending procedures should be activated.Typically, RTM transaction status is stored in a register such as a RTMcontrol and status register. The hardware of the processor evaluates thecontents of this register to determine if there is an RTM transactionoccurring. When there is an RTM transaction occurring, the RTMtransaction continues to process at 803.

When there is not an RTM transaction occurring, or RTM is not supported,a determination of if a current DSX nest count is less than a maximumnest count is made at 805. In some embodiments, a nest count register tostore the current nest count is provided by the YBEGIN instruction as anoperand. Alternatively, a dedicated nest count register may exist inhardware to be used to store the current nest count. The maximum nestcount is the maximum number of DSX starts (e.g., via a YBEGINinstruction) that can occur without a corresponding DSX end (e.g., via aYEND instruction).

When the current DSX nest count is greater than the maximum, an abortoccurs at 807. In some embodiments, an abort triggers a rollback usingrestoration circuitry such as DSX restoration circuitry 135. In otherembodiments, a YABORT instruction is executed as detailed below whichnot only performs a rollback to the fallback address, but also discardsspeculatively stored writes and resets the current nest count and setsthe DSX status to inactive. As detailed above, DSX status is typicallystored in a control register such as a DSX status and control register(DSXSR) shown in FIG. 1. However, other means such as a DSX status flagin a non-dedicated control/status register (such as a FLAGS register)may be utilized.

When the current nest count is not greater than the maximum, the currentDSX nest count is incremented at 809.

A determination of if a current DSX nest count is equal to one is madeat 811. When it is, in some embodiments, a fallback address iscalculated by adding the displacement value provided by the YBEGINinstruction to the address of the instruction following the YBEGINinstruction at 813. In embodiments where the YBEGIN instruction providedthe fallback address, then this calculation is not necessary.

At 815, the DSX status is set to active (if it needs to be) and the DSXtracking hardware is reset (for example, as detailed above). Forexample, as detailed earlier, a status for a DSX is typically stored inan accessible location such as a register such as the DSX status andcontrol register (DSXSR) discussed above with respect to FIG. 1.However, other means such as a DSX status flag in a non-dedicatedcontrol/status register (such as a FLAGS register) may be utilized. Thisregister may be checked by the hardware of the core to determine if aDSX was indeed taking place.

FIG. 9 illustrates an example of pseudo-code showing the execution of aninstruction such as a YBEGIN instruction.

YBEGIN with Stride Instruction

FIG. 10 illustrates an embodiment of an execution of an instruction forbeginning DSX. As will be detailed herein, this instruction is referredto as “YBEGIN WITH STRIDE” and is used to signal the beginning of a DSXregion. Of course, the instruction may be referred to by another name.In some embodiments, this execution is performed on one more hardwarecores of a hardware device such as a central processing unit (CPU),graphics processing unit (GPU), accelerated processing unit (APU),digital signal processor (DSP), etc. In other embodiments, the executionof the instruction is an emulation.

At 1001, a YBEGIN WITH STRIDE instruction is received/fetched. Forexample, the instruction is fetched from memory into an instructioncache or fetched from an instruction cache. The fetched instruction maytake one of several forms as detailed below.

FIG. 11 illustrates some exemplary embodiments of a YBEGIN WITH STRIDEinstruction format. In an embodiment, the YBEGIN WITH STRIDE instructionincludes an opcode (YBEGIN WITH STRIDE) and an operand to provide adisplacement for a fallback address which is where program executionshould go to handle a mis-speculation and a stride value operand asshown in 1101. In essence, the displacement is a portion of the fallbackaddress. In some embodiments, the displacement is provided as animmediate operand. In other embodiments, the displacement value isstored in a register or memory location operand. In some embodiments,the stride is provided as an immediate operand. In other embodiments,the stride is stored in a register or memory location operand. Dependingupon the YBEGIN WITH STRIDE implementation implicit operands for a DSXstatus register, a nesting count register, and/or a RTM status registerare used.

In another embodiment, the YBEGIN WITH STRIDE instruction includes notonly an opcode and displacement operand and a stride value operand, butalso an explicit operand for DSX status such as a DSX status register asshown in 1103. In some embodiments, the displacement is provided as animmediate operand. In other embodiments, the displacement value isstored in a register or memory location operand. In some embodiments,the stride is provided as an immediate operand. In other embodiments,the stride is stored in a register or memory location operand. Asdetailed earlier, the DSX status register may be a dedicated register, aflag in a register not dedicated to DSX status (such as an overallstatus register like a flag register), etc. Depending upon the YBEGINWITH STRIDE implementation implicit operands for a nesting countregister and/or a RTM status register are used.

In another embodiment, the YBEGIN WITH STRIDE instruction includes notonly an opcode, a displacement operand and a stride value operand, and astride value operand, but also an explicit operand for DSX nesting countsuch as a DSX nest count register as shown in 1105. In some embodiments,the displacement is provided as an immediate operand. In otherembodiments, the displacement value is stored in a register or memorylocation operand. In some embodiments, the stride is provided as animmediate operand. In other embodiments, the stride is stored in aregister or memory location operand. As detailed earlier, the DSX nestcount may be a dedicated register, a flag in a register not dedicated toDSX nest count (such as an overall status register). Depending upon theYBEGIN WITH STRIDE implementation implicit operands for a DSX statusregister and/or a RTM status register are used.

In another embodiment, the YBEGIN WITH STRIDE instruction includes notonly an opcode, displacement operand and a stride value operand, butalso explicit operands for DSX status such as a DSX status register andDSX nesting count such as a DSX nest count register as shown in 1107. Insome embodiments, the displacement is provided as an immediate operand.In other embodiments, the displacement value is stored in a register ormemory location operand. In some embodiments, the stride is provided asan immediate operand. In other embodiments, the stride is stored in aregister or memory location operand. As detailed earlier, the DSX statusregister may be a dedicated register, a flag in a register not dedicatedto DSX status (such as an overall status register like a flag register,etc.), and the DSX nest count may be a dedicated register, a flag in aregister not dedicated to DSX nest count (such as an overall statusregister. Depending upon the YBEGIN WITH STRIDE implementation animplicit operand for a RTM status register are used.

In another embodiment, the YBEGIN WITH STRIDE instruction includes notonly an opcode, displacement operand and a stride value operand, butexplicit operands for DSX status such as a DSX status register, DSXnesting count such as a DSX nest count register, and a RTM statusregister as shown in 409. In some embodiments, the displacement isprovided as an immediate operand. In other embodiments, the displacementvalue is stored in a register or memory location operand. In someembodiments, the stride is provided as an immediate operand. In otherembodiments, the stride is stored in a register or memory locationoperand. As detailed earlier, the DSX status register may be a dedicatedregister, a flag in a register not dedicated to DSX status (such as anoverall status register like a flag register, etc., and the DSX nestcount may be a dedicated register, a flag in a register not dedicated toDSX nest count (such as an overall status register).

Of course other variants of YBEGIN WITH STRIDE are possible. Forexample, instead of providing a displacement value, the instructionincludes the fallback address itself in either an immediate, register,or memory location.

Turning back to FIG. 10, the fetched/received YBEGIN WITH STRIDEinstruction is decoded at 1003. In some embodiments, the instruction isdecoded by a hardware decoder such as those detailed later. In someembodiments, the instruction is decoded into micro-operations(micro-ops). For example, some CISC based machines typically usemicro-operations that are derived from a macro-instruction. In otherembodiments, the decoding is a part of a software routine such as ajust-in-time compilation.

At 1005, any operand associated with the decoded YBEGIN WITH STRIDEinstruction is retrieved. For example, the data from one or more of aDSX register, DSX nest count register, and/or a RTM status register areretrieved.

The decoded YBEGIN WITH STRIDE instruction is executed at 1007. Inembodiments where the instruction is decoded into micro-ops, thesemicro-ops are executed. The execution of the decoded instruction causesthe hardware to do one or more of the following acts to be performed: 1)determine that an RTM transaction is active and begin that transaction;2) calculate a fallback address using the displacement value added tothe instruction pointer of the YBEGIN WITH STRIDE instruction; 3)increment the DSX nesting count; 4) abort; 5) set DSX status to active;6) reset DSX tracking hardware; and/or 7) provides the stride value tothe DSX hardware tracker.

Typically, upon a first instance of an YBEGIN WITH STRIDE instruction,if there is not an active RTM transaction, then the DSX status is set toactive, the DSX tracking hardware is reset (for example, as detailedabove using the provided stride value), and a fallback address iscalculated using the displacement value to start a DSX region. Asdetailed earlier, a status for a DSX is typically stored in anaccessible location such as a register such as the DSX status andcontrol register (DSXSR) discussed above with respect to FIG. 1.However, other means such as a DSX status flag in a non-dedicatedcontrol/status register (such as a FLAGS register) may be utilized.Resetting of the DSX tracking hardware was also previously described.

Typically, upon an instance of an YBEGIN WITH STRIDE instruction, ifthere is not an active RTM transaction, then the DSX status is set toactive, the DSX nest count is incremented (if the count is less than amax), the DSX tracking hardware is reset (for example, as detailed aboveusing the provided stride), and a fallback address is calculated usingthe displacement value to start a DSX region. As detailed earlier, astatus for a DSX is typically stored in an accessible location such as aregister such as the DSX status and control register (DSXSR) discussedabove with respect to FIG. 1. However, other means such as a DSX statusflag in a non-dedicated control/status register (such as a FLAGSregister) may be utilized. Resetting of the DSX tracking hardware wasalso previously described. As detailed earlier, a status for a DSX istypically stored in an accessible location such as a register such asthe DSX status and control register (DSXSR) discussed above with respectto FIG. 1. However, other means such as a DSX status flag in anon-dedicated control/status register (such as a FLAGS register) may beutilized. This register may be checked by the hardware of the core todetermine if a DSX was indeed taking place.

If there was some reason that the DSX cannot start, then one or more ofthe other potential actions takes place. For example, in someembodiments of processors that support RTM, if a RTM transaction wasactive then there should not have been a DSX active in the first placeand the RTM is pursued. If there is something wrong with the set up ofthe DSX in the first place (nest count not correct), then an abort willtake place. Additionally, in some embodiments, if there was no DSX thena fault is generated and no operations (a NOP) are performed. Regardlessof which act is performed, in most embodiments after that act the DSXstate is reset (if it was set) to indicate that there is no pending DSX.

FIG. 12 illustrates a detailed embodiment of an execution of aninstruction such as a YBEGIN WITH STRIDE instruction. For example, insome embodiments this flow is box 1007 of FIG. 10. In some embodiments,this execution is performed on one more hardware cores of a hardwaredevice such as a central processing unit (CPU), graphics processing unit(GPU), accelerated processing unit (APU), digital signal processor(DSP), etc. In other embodiments, the execution of the instruction is anemulation.

In some embodiments, for example in a processor that supports RTMtransactions, a determination of if a RTM transaction is occurring ismade at 1201. For example, in some embodiments of processors thatsupport RTM, if a RTM transaction was active then there should not havebeen a DSX active in the first place. In this instance, something wentwrong in the RTM transaction and its ending procedures should beactivated. Typically, RTM transaction status is stored in a registersuch as a RTM control and status register. The hardware of the processorevaluates the contents of this register to determine if there is an RTMtransaction occurring. When there is an RTM transaction occurring, theRTM transaction continues to process 1203.

When there is not an RTM transaction occurring, or RTM is not supported,a determination of if a current DSX nest count is less than a maximumnest count is made at 1205. In some embodiments, a nest count registerto store the current nest count is provided by the YBEGIN WITH STRIDEinstruction as an operand. Alternatively, a dedicated nest countregister may exist in hardware to be used to store the current nestcount. The maximum nest count is the maximum number of DSX starts (e.g.,via a YBEGIN instruction) that can occur without a corresponding DSX end(e.g., via a YEND instruction).

When the current nest count is greater than the maximum, an abort occursat 1207. In some embodiments, an abort triggers a rollback. In otherembodiments, a YABORT is performed as detailed below which not onlyperforms a rollback to the fallback address, but also discardsspeculatively stored writes and resets the current nest count and setsthe DSX status to inactive. As detailed above, DSX status is typicallystored in a control register such as a DSX status and control register(DSXSR) shown in FIG. 1. However, other means such as a DSX status flagin a non-dedicated control/status register (such as a FLAGS register)may be utilized.

When the current nest count is not greater than the maximum, the currentDSX nest count is incremented at 1209.

A determination of if a current DSX nest count is equal to one is madeat 1211. When it is, in some embodiments, a fallback address iscalculated by adding the displacement value provided by the YBEGIN WITHSTRIDE instruction to the address of the instruction following theYBEGIN WITH STRIDE instruction at 1213. In embodiments where the YBEGINWITH STRIDE instruction provided the fallback address, then thiscalculation is not necessary.

At 1215, the DSX status is set to active (if it needs to be) and the DSXtracking hardware is reset (for example, as detailed above includingusing the provided stride value). For example, as detailed earlier, astatus for a DSX is typically stored in an accessible location such as aregister such as the DSX status and control register (DSXSR) discussedabove with respect to FIG. 1. However, other means such as a DSX statusflag in a non-dedicated control/status register (such as a FLAGSregister) may be utilized. This register may be checked by the hardwareof the core to determine if a DSX was indeed taking place.

YCONTINUE Instruction

As a DSX comes to an end (for example, an iteration of a loop has runits course) without any issues, in some embodiments an instruction(YEND) is executed to indicate the end of a speculative region asdetailed below. In short, the execution of this instruction causes thecommitment of a current speculative state (all writes that have not beenwritten) and an exit from the current speculative region as will bediscussed below. Another iteration of the loop may then be started bycalling for another YBEGIN.

However, in some embodiments, an optimization to this cycle of YBEGIN,YEND, YBEGIN, etc. is available through the use of a continueinstruction to commit a current loop iteration when speculation is nolonger needed (e.g., when there is no conflict between stores). Thecontinue instruction also starts a new speculative loop iterationwithout the need for calling a YBEGIN.

FIG. 13 illustrates an embodiment of an execution of an instruction forcontinuing a DSX without ending it. As will be detailed herein, thisinstruction is referred to as “YCONTINUE” and is used to signal the endof a transaction. Of course, the instruction may be referred to byanother name.

In some embodiments, this execution is performed on one more hardwarecores of a hardware device such as a central processing unit (CPU),graphics processing unit (GPU), accelerated processing unit (APU),digital signal processor (DSP), etc. In other embodiments, the executionof the instruction is an emulation.

At 1301, an YCONTINUE instruction is received/fetched. For example, theinstruction is fetched from memory into an instruction cache or fetchedfrom an instruction cache. The fetched instruction may take one ofseveral forms.

FIG. 14 illustrates some exemplary embodiments of a YCONTINUEinstruction format. In an embodiment, the YCONTINUE instruction includesan opcode (YCONTINUE), but no explicit operands as shown in 1401.Depending upon the YCONTINUE implementation implicit operands for a DSXstatus register and nesting count register. As detailed earlier, the DSXnest count may be a dedicated register, a flag in a register notdedicated to DSX nest count (such as an overall status register), etc.Additionally, the DSX status register may be a dedicated register, aflag in a register not dedicated to DSX status (such as an overallstatus register like a flag register), etc.

In another embodiment, the YCONTINUE instruction includes not only anopcode, but an explicit operand for DSX status such as a DSX statusregister as shown in 1403. Depending upon the YCONTINUE implementationan implicit operand for nesting count register is used. As detailedearlier, the DSX nest count may be a dedicated register, a flag in aregister not dedicated to DSX nest count (such as an overall statusregister), etc. Additionally, the DSX status register may be a dedicatedregister, a flag in a register not dedicated to DSX status (such as anoverall status register like a flag register), etc.

In another embodiment, the YCONTINUE instruction includes not only anopcode, but an explicit operand for DSX nesting count such as a DSX nestcount register as shown in 1405. Depending upon the YCONTINUEimplementation implicit operand for a DSX status register is used. Asdetailed earlier, the DSX nest count may be a dedicated register, a flagin a register not dedicated to DSX nest count (such as an overall statusregister), etc. Additionally, the DSX status register may be a dedicatedregister, a flag in a register not dedicated to DSX status (such as anoverall status register like a flag register), etc.

In another embodiment, the YCONTINUE instruction includes not only anopcode, but an explicit operand for DSX status such as a DSX statusregister and DSX nesting count such as a DSX nest count register asshown in 1407. As detailed earlier, the DSX nest count may be adedicated register, a flag in a register not dedicated to DSX nest count(such as an overall status register), etc. Additionally, the DSX statusregister may be a dedicated register, a flag in a register not dedicatedto DSX status (such as an overall status register like a flag register),etc.

Turning back to FIG. 13, the fetched/received YCONTINUE instruction isdecoded at 1303. In some embodiments, the instruction is decoded by ahardware decoder such as those detailed later. In some embodiments, theinstruction is decoded into micro-operations (micro-ops). For example,some CISC based machines typically use micro-operations that are derivedfrom a macro-instruction. In other embodiments, the decoding is a partof a software routine such as a just-in-time compilation.

At 1305, any operand associated with the decoded YCONTINUE instructionis retrieved. For example, the data from one or more of a DSX registerand DSX nest count register are retrieved.

The decoded YCONTINUE instruction is executed at 1307. In embodimentswhere the instruction is decoded into micro-ops, these micro-ops areexecuted. The execution of the decoded instruction causes the hardwareto do one or more of the following acts to be performed: 1) determinethat make speculative writes associated with the DSX are to be committedas speculation is no longer needed and commit them, and start newspeculative loop iteration (such as new DSX region); and/or 2) nooperation.

The first of these acts (making speculative writes final and starting anew speculative loop iteration) may be performed by DSX checkinghardware detailed earlier. In this act all of the speculative writesassociated with the loop iteration of the DSX are committed (stored suchthat they are accessible outside of the DSX), but unlike a YENDinstruction, the DSX status is not set to indicate that a DSX does notexist. For example, all writes associated with the DSX (such as storedin cache, registers, or memory) are committed such that they arefinalized and visible outside of the DSX. Typically, a DSX commit willnot happen unless the DSX nest count is one. Otherwise, in someembodiments, then a nop is performed.

If a DSX is not active, then a nop may be performed in some embodiments.

FIG. 15 illustrates a detailed embodiment of an execution of aninstruction such as a YCONTINUE instruction. For example, in someembodiments this flow is box 1307 of FIG. 13. In some embodiments, thisexecution is performed on one more hardware cores of a hardware devicesuch as a central processing unit (CPU), graphics processing unit (GPU),accelerated processing unit (APU), digital signal processor (DSP), etc.In other embodiments, the execution of the instruction is an emulation.

A determination of if a DSX is active is made at 1501. As detailedabove, DSX status is typically stored in a control register such as aDSX status and control register (DSXSR) shown in FIG. 1. However, othermeans such as a DSX status flag in a non-dedicated control/statusregister (such as a FLAGS register) may be utilized. Regardless of wherethe status is stored, the location is checked by the hardware of theprocessor to determine if a DSX was indeed taking place.

When there is not a DSX occurring, a no op is performed at 1503.

When there is a DSX occurring, a determination of if the DSX nest countis equal to one is made at 1505. As detailed above, DSX nest count istypically stored in a nesting count register. When the DSX nest count isnot one, a nop is performed at 507. When the DSX nest count is one, acommit and DSX restart is done at 1509. When a commit and DSX restarthappens, in some embodiments, one or more of the following occur: 1) DSXtracking hardware is reset (for example, as detailed above), 2) afallback address is calculated, and 3) a commit of speculativelyexecuted instructions (writes) of a previous speculative region is made.

FIG. 16 illustrates an example of pseudo-code showing the execution ofan instruction such as a YCONTINUE instruction.

YBORT Instruction

At times there are issues within a DSX that require the DSX to abort(such as a mis-speculation). FIG. 17 illustrates an embodiment of anexecution of an instruction for aborting a DSX. As will be detailedherein, this instruction is referred to as “YABORT.” Of course, theinstruction may be referred to by another name. In some embodiments,this execution is performed on one more hardware cores of a hardwaredevice such as a central processing unit (CPU), graphics processing unit(GPU), accelerated processing unit (APU), digital signal processor(DSP), etc. In other embodiments, the execution of the instruction is anemulation.

At 1701, a YABORT instruction is received/fetched. For example, theinstruction is fetched from memory into an instruction cache or fetchedfrom an instruction cache. The fetched instruction may take one ofseveral forms as detailed below.

FIG. 18 illustrates some exemplary embodiments of a YABORT instructionformat. In an embodiment, the YABORT instruction includes only an opcode(YABORT) as shown in 1801. Depending upon the YABORT implementationimplicit operands for a DSX status register and/or a RTM status registerare used. As detailed earlier, the DSX status register may be adedicated register, a flag in a register not dedicated to DSX status(such as an overall status register like a flag register), etc.

In another embodiment, the YABORT instruction includes not only anopcode, but also an explicit operand for a DSX status register such as aDSX status register as shown in 1803. As detailed earlier, the DSXstatus register may be a dedicated register, a flag in a register notdedicated to DSX status (such as an overall status register like a flagregister), etc. Depending upon the YABORT implementation an implicitoperands for a RTM status register is used.

In another embodiment, the YABORT instruction includes not only anopcode, but also explicit operands for a DSX status register such as aDSX status register as and a RTM status register as shown in 1805. Asdetailed earlier, the DSX status register may be a dedicated register, aflag in a register not dedicated to DSX status (such as an overallstatus register like a flag register), etc.

Turning back to FIG. 17, the fetched/received YABORT instruction isdecoded at 1703. In some embodiments, the instruction is decoded by ahardware decoder such as those detailed later. In some embodiments, theinstruction is decoded into micro-operations (micro-ops). For example,some CISC based machines typically use micro-operations that are derivedfrom a macro-instruction. In other embodiments, the decoding is a partof a software routine such as a just-in-time compilation.

At 1705, any operand associated with the decoded YABORT instruction isretrieved. For example, the data from one or more of a DSX registerand/or a RTM status register are retrieved.

The decoded YABORT instruction is executed at 1707. In embodiments wherethe instruction is decoded into micro-ops, these micro-ops are executed.The execution of the decoded instruction causes the hardware to do oneor more of the following acts to be performed: 1) determine that an RTMtransaction is active and abort the RTM transaction; 2) determine that aDSX is not active and perform a no operation; and/or 3) abort the DSX byresetting any DSX nest count, discarding all speculatively executedwrites, setting the DSX status to inactive, and rolling back executionto a fallback address.

Regarding the first act, RTM status is typically stored in a RTM statusand control register. When this register indicates that an RTMtransaction is taking place, an YABORT instruction should not have beenexecuted. As such, there was an issue with the RTM transaction and itshould abort.

Regarding the second and third acts, as detailed earlier, a status for aDSX is typically stored in an accessible location such as a registersuch as the DSX status and control register (DSXSR) discussed above withrespect to FIG. 1. However, other means such as a DSX status flag in anon-dedicated control/status register (such as a FLAGS register) may beutilized. This register may be checked by the hardware of the core todetermine if a DSX was indeed taking place. When there is no DSXindicated by this register, then there would be no reason to execute aYABORT instruction and as such a no operation (or similar operation) isperformed. When there is a DSX indicated by this register, then DSXabort processing occurs including resetting the DSX tracking hardware,discarding all stored speculatively executed writes, and resetting theDSX status to be inactive, and rolling back execution.

FIG. 19 illustrates a detailed embodiment of an execution of aninstruction such as a YABORT instruction. For example, in someembodiments this flow is box 1707 of FIG. 17. In some embodiments, thisexecution is performed on one more hardware cores of a hardware devicesuch as a central processing unit (CPU), graphics processing unit (GPU),accelerated processing unit (APU), digital signal processor (DSP), etc.In other embodiments, the execution of the instruction is an emulation.

In some embodiments, for example in a processor that supports RTMtransactions, a determination of if a RTM transaction is occurring ismade at 1901. For example, in some embodiments of processors thatsupport RTM, if a RTM transaction was active then there should not havebeen a DSX active in the first place. In this instance, something wentwrong in the RTM transaction and its ending procedures should beactivated. Typically, RTM transaction status is stored in a registersuch as a RTM control and status register. The hardware of the processorevaluates the contents of this register to determine if there is an RTMtransaction occurring. When there is an RTM transaction occurring, theRTM transaction continues to process 1903.

When there is not an RTM transaction occurring, or RTM is not supported,a determination of if a DSX is active is made at 1905. A status for aDSX is typically stored in an accessible location such as the DSX statusand control register (DSXSR) discussed above with respect to FIG. 1.However, other means such as a DSX status flag in a non-dedicatedcontrol/status register (such as a FLAGS register) may be utilized. Thisregister may be checked by the hardware of the core to determine if aDSX was taking place.

When there is no DSX indicated by this register, then a nop is performedat 1907. When there is a DSX indicated by this register, then DSX abortprocessing occurs at 1909 including resetting the DSX tracking hardware,discarding all stored speculatively executed writes, and resetting theDSX status to be inactive, and rolling back execution.

FIG. 20 illustrates an example of pseudo-code showing the execution ofan instruction such as a YABORT instruction.

YTEST Instruction

Generally it is desirable for software to know if a DSX is active or notbefore starting a new DSX speculative region. FIG. 21 illustrates anembodiment of an execution of an instruction for testing the status ofDSX. As will be detailed herein, this instruction is referred to as“YTEST” and is used to provide an indication of DSX active through theuse of a flag. Of course, the instruction may be referred to by anothername.

In some embodiments, this execution is performed on one more hardwarecores of a hardware device such as a central processing unit (CPU),graphics processing unit (GPU), accelerated processing unit (APU),digital signal processor (DSP), etc. In other embodiments, the executionof the instruction is an emulation.

At 2101, a YTEST instruction is received/fetched. For example, theinstruction is fetched from memory into an instruction cache or fetchedfrom an instruction cache. The fetched instruction may take one ofseveral forms. FIG. 22 illustrates some exemplary embodiments of a YTESTinstruction format. In an embodiment, the YTEST instruction includes anopcode (YTEST), but no explicit operands as shown in 2201. Implicitoperands for DSX status register and a flag register are used. Asdetailed earlier, the DSX status register may be a dedicated register, aflag in a register not dedicated to DSX status (such as an overallstatus register like a flag register, etc.). Exemplary flag registersinclude an EFLAGS register. In particular, the flag register is to storea zero flag (ZF).

In another embodiment, the YTEST instruction includes not only anopcode, but an explicit operand for DSX status such as a DSX statusregister as shown in 2203. As detailed earlier, the DSX status registermay be a dedicated register, a flag in a register not dedicated to DSXstatus (such as an overall status register like a flag register, etc.).An implicit operand for a flag register is used. Exemplary flagregisters include an EFLAGS register. In particular, the flag registeris to store a zero flag (ZF).

In another embodiment, the YTEST instruction includes not only anopcode, but an explicit operand for a flag register as shown in 2205.Exemplary flags registers include an EFLAGS register. In particular, theflag register is to store a zero flag (ZF). An implicit operand for aDSX status register is used. As detailed earlier, the DSX statusregister may be a dedicated register, a flag in a register not dedicatedto DSX status (such as an overall status register like a flag register,etc.).

In another embodiment, the YTEST instruction includes not only anopcode, but an explicit operand for DSX status such as a DSX statusregister and a flag register as shown in 2207. As detailed earlier, theDSX status register may be a dedicated register, a flag in a registernot dedicated to DSX status (such as an overall status register like aflag register, etc.). An implicit operand for a flag register is used.Exemplary flag registers include an EFLAGS register. In particular, theflag register is to store a zero flag (ZF).

Turning back to FIG. 21, the fetched/received YTEST instruction isdecoded at 2103. In some embodiments, the instruction is decoded by ahardware decoder such as those detailed later. In some embodiments, theinstruction is decoded into micro-operations (micro-ops). For example,some CISC based machines typically use micro-operations that are derivedfrom a macro-instruction. In other embodiments, the decoding is a partof a software routine such as a just-in-time compilation.

At 2105, any operand associated with the decoded YTEST instruction isretrieved. For example, the data from the DSX status register isretrieved.

The decoded YTEST instruction is executed at 2107. In embodiments wherethe instruction is decoded into micro-ops, these micro-ops are executed.The execution of the decoded instruction causes the hardware to do oneor more of the following acts to be performed: 1) determine that the DSXstatus register indicates that a DSX is active and if so set the zeroflag in the flag register to 0 or 2) determine that the DSX statusregister indicates that a DSX is not active and if so set the zero flagin the flag register to 1. Of course, while the zero flag is used toshow DSX active status, other flags are used depending upon theembodiment.

FIG. 23 illustrates an example of pseudo-code showing the execution ofan instruction such as a YTEST instruction.

YEND Instruction

As a DSX comes to an end (for example, an iteration of a loop has runits course) without any issues, in some embodiments an instruction isexecuted to indicate the end of a speculative region. In short, theexecution of this instruction causes the commitment of a currentspeculative state (all writes that have not been written) and an exitfrom the current speculative region.

FIG. 24 illustrates an embodiment of an execution of an instruction forending a DSX. As will be detailed herein, this instruction is referredto as “YEND” and is used to signal the end of a DSX. Of course, theinstruction may be referred to by another name.

In some embodiments, this execution is performed on one more hardwarecores of a hardware device such as a central processing unit (CPU),graphics processing unit (GPU), accelerated processing unit (APU),digital signal processor (DSP), etc. In other embodiments, the executionof the instruction is an emulation.

At 2401, a YEND instruction is received/fetched. For example, theinstruction is fetched from memory into an instruction cache or fetchedfrom an instruction cache. The fetched instruction may take one ofseveral forms. FIG. 25 illustrates some exemplary embodiments of a YENDinstruction format. In an embodiment, the YEND instruction includes anopcode (YEND), but no explicit operands as shown in 2501. Depending uponthe YEND implementation implicit register operands for DSX status,nesting count, and/or RTM status are used.

In another embodiment, the YEND instruction includes not only an opcode,but an explicit operand for DSX status such as a DSX status register asshown in 2503. As detailed earlier, the DSX status register may be adedicated register, a flag in a register not dedicated to DSX status(such as an overall status register like a flag register, etc.).Depending upon the YEND implementation implicit register operands fornesting count and/or RTM status are used.

In another embodiment, the YEND instruction includes not only an opcode,but an explicit operand for DSX nesting count such as a DSX nest countregister as shown in 2505. As detailed earlier, the DSX nest count maybe a dedicated register, a flag in a register not dedicated to DSX nestcount (such as an overall status register). Depending upon the YENDimplementation implicit register operands for DSX status and/or RTMstatus are used.

In another embodiment, the YEND instruction includes not only an opcode,but an explicit operand for DSX status such as a DSX status register andDSX nesting count such as a DSX nest count register as shown in 2507. Asdetailed earlier, the DSX status register may be a dedicated register, aflag in a register not dedicated to DSX status (such as an overallstatus register like a flag register, etc.), and the DSX nest count maybe a dedicated register, a flag in a register not dedicated to DSX nestcount (such as an overall status register). Depending upon the YENDimplementation an implicit operand for a RTM status register is used.

In another embodiment, the YEND instruction includes not only an opcode,but an explicit operand for DSX status such as a DSX status register,DSX nesting count such as a DSX nest count register, and RTM status asshown in 2509. As detailed earlier, the DSX status register may be adedicated register, a flag in a register not dedicated to DSX status(such as an overall status register like a flag register, etc.), and theDSX nest count may be a dedicated register, a flag in a register notdedicated to DSX nest count (such as an overall status register).

Turning back to FIG. 24, the fetched/received YEND instruction isdecoded at 2403. In some embodiments, the instruction is decoded by ahardware decoder such as those detailed later. In some embodiments, theinstruction is decoded into micro-operations (micro-ops). For example,some CISC based machines typically use micro-operations that are derivedfrom a macro-instruction. In other embodiments, the decoding is a partof a software routine such as a just-in-time compilation.

At 2405, any operand associated with the decoded YEND instruction isretrieved. For example, the data from one or more of a DSX register, DSXnest count register, and/or a RTM status register are retrieved.

The decoded YEND instruction is executed at 2407. In embodiments wherethe instruction is decoded into micro-ops, these micro-ops are executed.The execution of the decoded instruction causes the hardware to do oneor more of the following acts to be performed: 1) make speculativewrites associated with the DSX final (commit them); 2) signal a fault(such as a general protection fault) and perform no operation; 3) abortthe DSX; and/or 4) end a RTM transaction.

The first of these acts (making speculative writes final) causes all ofthe speculative writes associated with the DSX to be committed (storedsuch that they are accessible outside of the DSX) and the DSX status isset to indicate that a DSX does not exist in a DSX status register. Forexample, all writes associated with the DSX (such as stored in cache,registers, or memory) are committed such that they are finalized andvisible outside of the DSX. Typically, a DSX cannot be finalized unlessthe nest count for that speculation is zero. If the nest count isgreater than zero, then in some embodiments, a NOP is performed.

If there was some reason that the DSX cannot be finalized, then one ormore of the other three potential actions takes place. For example, insome embodiments of processors that support RTM, if a RTM transactionwas active then there should not have been a DSX active in the firstplace. In this instance, something went wrong in the RTM transaction andits ending procedures should be activated as indicated by the fourth actabove.

In some embodiments, if there was no DSX then a fault is generated andno operation (NOP) is performed. For example, as detailed earlier, astatus for a DSX is typically stored in an accessible location such as aregister such as the DSX status and control register (DSXSR) discussedabove with respect to FIG. 1. However, other means such as a DSX statusflag in a non-dedicated control/status register (such as a FLAGSregister) may be utilized. This register may be checked by the hardwareof the core to determine if a DSX was indeed taking place.

In some embodiments, if there is a failure in the committing of thetransaction, then an abort procedure is implemented. For example, insome embodiments of processors that support RTM, the RTM abortprocedures is activated.

Regardless of which act is performed, in most embodiments, after thatact the DSX state is reset (if it was set) to indicate that there is nopending DSX.

FIG. 26 illustrates a detailed embodiment of an execution of aninstruction such as a YEND instruction. For example, in some embodimentsthis flow is box 2407 of FIG. 24. In some embodiments, this execution isperformed on one more hardware cores of a hardware device such as acentral processing unit (CPU), graphics processing unit (GPU),accelerated processing unit (APU), digital signal processor (DSP), etc.In other embodiments, the execution of the instruction is an emulation.

In some embodiments, for example in a processor that supports RTMtransactions, a determination of if a RTM transaction is occurring ismade at 2601. For example, in some embodiments of processors thatsupport RTM, if a RTM transaction was active then there should not havebeen a DSX active in the first place. In this instance, something wentwrong in the RTM transaction and its ending procedures should beactivated. Typically, RTM transaction status is stored in a registersuch as a RTM control and status register. The hardware of the processorevaluates the contents of this register to determine if there is an RTMtransaction occurring.

When there is an RTM transaction occurring, a call to end that RTMtransaction is made at 2603. For example, an instruction to end an RTMtransaction is called and executed. An example of such an instruction isXEND.

When there is not an RTM transaction occurring, a determination of if aDSX is active is made at 2605. As detailed above, DSX status istypically stored in a control register such as a DSX status and controlregister (DSXSR) shown in FIG. 1. However, other means such as a DSXstatus flag in a non-dedicated control/status register (such as a FLAGSregister) may be utilized. Regardless of where the status is stored, thelocation is checked by the hardware of the processor to determine if aDSX was indeed taking place.

When there is not a DSX occurring, a fault is generated at 2607. Forexample, a general protection fault is generated. Additionally, in someembodiments a no operation (nop) is performed.

When there is a DSX occurring, a DSX nest count is decremented at 2609.For example, a stored DSX nest count stored in a DSX nest count registersuch as detailed above is decremented.

A determination of if the DSX nest count is equal to zero is made at2611. As detailed above, DSX nest count is typically stored in aregister. When the DSX nest count is not zero, in some embodiments, aNOP is performed. When the DSX nest count is zero, the current DSX'sspeculative state is made final and committed at 2615.

A determination of if the commitment was successful is made at 2617. Forexample, was there an error in storing? If not, then the DSX is abortedat 2621. When the commitment was successful, a DSX status indication(such as stored in a DSX status and control register) is set to indicatethat there is no DSX active at 2619. In some embodiments, the setting ofthis indication occurs after the generation of a fault 2607 or the abortof the DSX 2621.

FIG. 27 illustrates an example of pseudo-code showing the execution ofan instruction such as a YEND instruction.

Discussed below are embodiments of instruction formats and executionresources to execute the above described instructions.

An instruction set includes one or more instruction formats. A giveninstruction format defines various fields (number of bits, location ofbits) to specify, among other things, the operation to be performed(opcode) and the operand(s) on which that operation is to be performed.Some instruction formats are further broken down though the definitionof instruction templates (or subformats). For example, the instructiontemplates of a given instruction format may be defined to have differentsubsets of the instruction format's fields (the included fields aretypically in the same order, but at least some have different bitpositions because there are less fields included) and/or defined to havea given field interpreted differently. Thus, each instruction of an ISAis expressed using a given instruction format (and, if defined, in agiven one of the instruction templates of that instruction format) andincludes fields for specifying the operation and the operands. Forexample, an exemplary ADD instruction has a specific opcode and aninstruction format that includes an opcode field to specify that opcodeand operand fields to select operands (source1/destination and source2);and an occurrence of this ADD instruction in an instruction stream willhave specific contents in the operand fields that select specificoperands. A set of SIMD extensions referred to the Advanced VectorExtensions (AVX) (AVX1 and AVX2) and using the Vector Extensions (VEX)coding scheme, has been, has been released and/or published (e.g., seeIntel® 64 and IA-32 Architectures Software Developers Manual, October2011; and see Intel® Advanced Vector Extensions Programming Reference,June 2011).

Exemplary Instruction Formats

Embodiments of the instruction(s) described herein may be embodied indifferent formats. Additionally, exemplary systems, architectures, andpipelines are detailed below. Embodiments of the instruction(s) may beexecuted on such systems, architectures, and pipelines, but are notlimited to those detailed.

Generic Vector Friendly Instruction Format

A vector friendly instruction format is an instruction format that issuited for vector instructions (e.g., there are certain fields specificto vector operations). While embodiments are described in which bothvector and scalar operations are supported through the vector friendlyinstruction format, alternative embodiments use only vector operationsthe vector friendly instruction format.

FIGS. 28A-28B are block diagrams illustrating a generic vector friendlyinstruction format and instruction templates thereof according toembodiments of the invention. FIG. 28A is a block diagram illustrating ageneric vector friendly instruction format and class A instructiontemplates thereof according to embodiments of the invention; while FIG.28B is a block diagram illustrating the generic vector friendlyinstruction format and class B instruction templates thereof accordingto embodiments of the invention. Specifically, a generic vector friendlyinstruction format 2800 for which are defined class A and class Binstruction templates, both of which include no memory access 2805instruction templates and memory access 2820 instruction templates. Theterm generic in the context of the vector friendly instruction formatrefers to the instruction format not being tied to any specificinstruction set.

While embodiments of the invention will be described in which the vectorfriendly instruction format supports the following: a 64 byte vectoroperand length (or size) with 32 bit (4 byte) or 64 bit (8 byte) dataelement widths (or sizes) (and thus, a 64 byte vector consists of either16 doubleword-size elements or alternatively, 8 quadword-size elements);a 64 byte vector operand length (or size) with 16 bit (2 byte) or 8 bit(1 byte) data element widths (or sizes); a 32 byte vector operand length(or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit (2 byte), or 8bit (1 byte) data element widths (or sizes); and a 16 byte vectoroperand length (or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit(2 byte), or 8 bit (1 byte) data element widths (or sizes); alternativeembodiments may support more, less and/or different vector operand sizes(e.g., 256 byte vector operands) with more, less, or different dataelement widths (e.g., 128 bit (16 byte) data element widths).

The class A instruction templates in FIG. 28A include: 1) within the nomemory access 2805 instruction templates there is shown a no memoryaccess, full round control type operation 2810 instruction template anda no memory access, data transform type operation 2815 instructiontemplate; and 2) within the memory access 2820 instruction templatesthere is shown a memory access, temporal 2825 instruction template and amemory access, non-temporal 2830 instruction template. The class Binstruction templates in FIG. 28B include: 1) within the no memoryaccess 2805 instruction templates there is shown a no memory access,write mask control, partial round control type operation 2812instruction template and a no memory access, write mask control, vsizetype operation 2817 instruction template; and 2) within the memoryaccess 2820 instruction templates there is shown a memory access, writemask control 2827 instruction template.

The generic vector friendly instruction format 2800 includes thefollowing fields listed below in the order illustrated in FIGS. 28A-28B.

Format field 2840—a specific value (an instruction format identifiervalue) in this field uniquely identifies the vector friendly instructionformat, and thus occurrences of instructions in the vector friendlyinstruction format in instruction streams. As such, this field isoptional in the sense that it is not needed for an instruction set thathas only the generic vector friendly instruction format.

Base operation field 2842—its content distinguishes different baseoperations.

Register index field 2844—its content, directly or through addressgeneration, specifies the locations of the source and destinationoperands, be they in registers or in memory. These include a sufficientnumber of bits to select N registers from a P×Q (e.g. 32×512, 16×128,32×1024, 64×1024) register file. While in one embodiment N may be up tothree sources and one destination register, alternative embodiments maysupport more or less sources and destination registers (e.g., maysupport up to two sources where one of these sources also acts as thedestination, may support up to three sources where one of these sourcesalso acts as the destination, may support up to two sources and onedestination).

Modifier field 2846—its content distinguishes occurrences ofinstructions in the generic vector instruction format that specifymemory access from those that do not; that is, between no memory access2805 instruction templates and memory access 2820 instruction templates.Memory access operations read and/or write to the memory hierarchy (insome cases specifying the source and/or destination addresses usingvalues in registers), while non-memory access operations do not (e.g.,the source and destinations are registers). While in one embodiment thisfield also selects between three different ways to perform memoryaddress calculations, alternative embodiments may support more, less, ordifferent ways to perform memory address calculations.

Augmentation operation field 2850—its content distinguishes which one ofa variety of different operations to be performed in addition to thebase operation. This field is context specific. In one embodiment of theinvention, this field is divided into a class field 2868, an alpha field2852, and a beta field 2854. The augmentation operation field 2850allows common groups of operations to be performed in a singleinstruction rather than 2, 3, or 4 instructions.

Scale field 2860—its content allows for the scaling of the index field'scontent for memory address generation (e.g., for address generation thatuses 2^(scale)*index+base).

Displacement Field 2862A—its content is used as part of memory addressgeneration (e.g., for address generation that uses2^(scale)*index+base+displacement).

Displacement Factor Field 2862B (note that the juxtaposition ofdisplacement field 2862A directly over displacement factor field 2862Bindicates one or the other is used)—its content is used as part ofaddress generation; it specifies a displacement factor that is to bescaled by the size of a memory access (N)—where N is the number of bytesin the memory access (e.g., for address generation that uses2^(scale)*index+base+scaled displacement). Redundant low-order bits areignored and hence, the displacement factor field's content is multipliedby the memory operands total size (N) in order to generate the finaldisplacement to be used in calculating an effective address. The valueof N is determined by the processor hardware at runtime based on thefull opcode field 2874 (described later herein) and the datamanipulation field 2854C. The displacement field 2862A and thedisplacement factor field 2862B are optional in the sense that they arenot used for the no memory access 2805 instruction templates and/ordifferent embodiments may implement only one or none of the two.

Data element width field 2864—its content distinguishes which one of anumber of data element widths is to be used (in some embodiments for allinstructions; in other embodiments for only some of the instructions).This field is optional in the sense that it is not needed if only onedata element width is supported and/or data element widths are supportedusing some aspect of the opcodes.

Write mask field 2870—its content controls, on a per data elementposition basis, whether that data element position in the destinationvector operand reflects the result of the base operation andaugmentation operation. Class A instruction templates supportmerging-writemasking, while class B instruction templates support bothmerging- and zeroing-writemasking. When merging, vector masks allow anyset of elements in the destination to be protected from updates duringthe execution of any operation (specified by the base operation and theaugmentation operation); in other one embodiment, preserving the oldvalue of each element of the destination where the corresponding maskbit has a 0. In contrast, when zeroing vector masks allow any set ofelements in the destination to be zeroed during the execution of anyoperation (specified by the base operation and the augmentationoperation); in one embodiment, an element of the destination is set to 0when the corresponding mask bit has a 0 value. A subset of thisfunctionality is the ability to control the vector length of theoperation being performed (that is, the span of elements being modified,from the first to the last one); however, it is not necessary that theelements that are modified be consecutive. Thus, the write mask field2870 allows for partial vector operations, including loads, stores,arithmetic, logical, etc. While embodiments of the invention aredescribed in which the write mask field's 2870 content selects one of anumber of write mask registers that contains the write mask to be used(and thus the write mask field's 2870 content indirectly identifies thatmasking to be performed), alternative embodiments instead or additionalallow the mask write field's 2870 content to directly specify themasking to be performed.

Immediate field 2872—its content allows for the specification of animmediate. This field is optional in the sense that is it not present inan implementation of the generic vector friendly format that does notsupport immediate and it is not present in instructions that do not usean immediate.

Class field 2868—its content distinguishes between different classes ofinstructions. With reference to FIGS. 28A-B, the contents of this fieldselect between class A and class B instructions. In FIGS. 28A-B, roundedcorner squares are used to indicate a specific value is present in afield (e.g., class A 2868A and class B 2868B for the class field 2868respectively in FIGS. 28A-B).

Instruction Templates of Class A

In the case of the non-memory access 2805 instruction templates of classA, the alpha field 2852 is interpreted as an RS field 2852A, whosecontent distinguishes which one of the different augmentation operationtypes are to be performed (e.g., round 2852A.1 and data transform2852A.2 are respectively specified for the no memory access, round typeoperation 2810 and the no memory access, data transform type operation2815 instruction templates), while the beta field 2854 distinguisheswhich of the operations of the specified type is to be performed. In theno memory access 2805 instruction templates, the scale field 2860, thedisplacement field 2862A, and the displacement scale filed 2862B are notpresent.

No-Memory Access Instruction Templates—Full Round Control Type Operation

In the no memory access full round control type operation 2810instruction template, the beta field 2854 is interpreted as a roundcontrol field 2854A, whose content(s) provide static rounding. While inthe described embodiments of the invention the round control field 2854Aincludes a suppress all floating point exceptions (SAE) field 2856 and around operation control field 2858, alternative embodiments may supportmay encode both these concepts into the same field or only have one orthe other of these concepts/fields (e.g., may have only the roundoperation control field 2858).

SAE field 2856—its content distinguishes whether or not to disable theexception event reporting; when the SAE field's 2856 content indicatessuppression is enabled, a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler.

Round operation control field 2858—its content distinguishes which oneof a group of rounding operations to perform (e.g., Round-up,Round-down, Round-towards-zero and Round-to-nearest). Thus, the roundoperation control field 2858 allows for the changing of the roundingmode on a per instruction basis. In one embodiment of the inventionwhere a processor includes a control register for specifying roundingmodes, the round operation control field's 2850 content overrides thatregister value.

No Memory Access Instruction Templates—Data Transform Type Operation

In the no memory access data transform type operation 2815 instructiontemplate, the beta field 2854 is interpreted as a data transform field2854B, whose content distinguishes which one of a number of datatransforms is to be performed (e.g., no data transform, swizzle,broadcast).

In the case of a memory access 2820 instruction template of class A, thealpha field 2852 is interpreted as an eviction hint field 2852B, whosecontent distinguishes which one of the eviction hints is to be used (inFIG. 28A, temporal 2852B.1 and non-temporal 2852B.2 are respectivelyspecified for the memory access, temporal 2825 instruction template andthe memory access, non-temporal 2830 instruction template), while thebeta field 2854 is interpreted as a data manipulation field 2854C, whosecontent distinguishes which one of a number of data manipulationoperations (also known as primitives) is to be performed (e.g., nomanipulation; broadcast; up conversion of a source; and down conversionof a destination). The memory access 2820 instruction templates includethe scale field 2860, and optionally the displacement field 2862A or thedisplacement scale field 2862B.

Vector memory instructions perform vector loads from and vector storesto memory, with conversion support. As with regular vector instructions,vector memory instructions transfer data from/to memory in a dataelement-wise fashion, with the elements that are actually transferred isdictated by the contents of the vector mask that is selected as thewrite mask.

Memory Access Instruction Templates—Temporal

Temporal data is data likely to be reused soon enough to benefit fromcaching. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.

Memory Access Instruction Templates—Non-Temporal

Non-temporal data is data unlikely to be reused soon enough to benefitfrom caching in the 1st-level cache and should be given priority foreviction. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.

Instruction Templates of Class B

In the case of the instruction templates of class B, the alpha field2852 is interpreted as a write mask control (Z) field 2852C, whosecontent distinguishes whether the write masking controlled by the writemask field 2870 should be a merging or a zeroing.

In the case of the non-memory access 2805 instruction templates of classB, part of the beta field 2854 is interpreted as an RL field 2857A,whose content distinguishes which one of the different augmentationoperation types are to be performed (e.g., round 2857A.1 and vectorlength (VSIZE) 2857A.2 are respectively specified for the no memoryaccess, write mask control, partial round control type operation 2812instruction template and the no memory access, write mask control, VSIZEtype operation 2817 instruction template), while the rest of the betafield 2854 distinguishes which of the operations of the specified typeis to be performed. In the no memory access 2805 instruction templates,the scale field 2860, the displacement field 2862A, and the displacementscale filed 2862B are not present.

In the no memory access, write mask control, partial round control typeoperation 2810 instruction template, the rest of the beta field 2854 isinterpreted as a round operation field 2859A and exception eventreporting is disabled (a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler).

Round operation control field 2859A—just as round operation controlfield 2858, its content distinguishes which one of a group of roundingoperations to perform (e.g., Round-up, Round-down, Round-towards-zeroand Round-to-nearest). Thus, the round operation control field 2859Aallows for the changing of the rounding mode on a per instruction basis.In one embodiment of the invention where a processor includes a controlregister for specifying rounding modes, the round operation controlfield's 2850 content overrides that register value.

In the no memory access, write mask control, VSIZE type operation 2817instruction template, the rest of the beta field 2854 is interpreted asa vector length field 2859B, whose content distinguishes which one of anumber of data vector lengths is to be performed on (e.g., 128, 256, or512 byte).

In the case of a memory access 2820 instruction template of class B,part of the beta field 2854 is interpreted as a broadcast field 2857B,whose content distinguishes whether or not the broadcast type datamanipulation operation is to be performed, while the rest of the betafield 2854 is interpreted the vector length field 2859B. The memoryaccess 2820 instruction templates include the scale field 2860, andoptionally the displacement field 2862A or the displacement scale field2862B.

With regard to the generic vector friendly instruction format 2800, afull opcode field 2874 is shown including the format field 2840, thebase operation field 2842, and the data element width field 2864. Whileone embodiment is shown where the full opcode field 2874 includes all ofthese fields, the full opcode field 2874 includes less than all of thesefields in embodiments that do not support all of them. The full opcodefield 2874 provides the operation code (opcode).

The augmentation operation field 2850, the data element width field2864, and the write mask field 2870 allow these features to be specifiedon a per instruction basis in the generic vector friendly instructionformat.

The combination of write mask field and data element width field createtyped instructions in that they allow the mask to be applied based ondifferent data element widths.

The various instruction templates found within class A and class B arebeneficial in different situations. In some embodiments of theinvention, different processors or different cores within a processormay support only class A, only class B, or both classes. For instance, ahigh performance general purpose out-of-order core intended forgeneral-purpose computing may support only class B, a core intendedprimarily for graphics and/or scientific (throughput) computing maysupport only class A, and a core intended for both may support both (ofcourse, a core that has some mix of templates and instructions from bothclasses but not all templates and instructions from both classes iswithin the purview of the invention). Also, a single processor mayinclude multiple cores, all of which support the same class or in whichdifferent cores support different class. For instance, in a processorwith separate graphics and general purpose cores, one of the graphicscores intended primarily for graphics and/or scientific computing maysupport only class A, while one or more of the general purpose cores maybe high performance general purpose cores with out of order executionand register renaming intended for general-purpose computing thatsupport only class B. Another processor that does not have a separategraphics core, may include one more general purpose in-order orout-of-order cores that support both class A and class B. Of course,features from one class may also be implement in the other class indifferent embodiments of the invention. Programs written in a high levellanguage would be put (e.g., just in time compiled or staticallycompiled) into an variety of different executable forms, including: 1) aform having only instructions of the class(es) supported by the targetprocessor for execution; or 2) a form having alternative routineswritten using different combinations of the instructions of all classesand having control flow code that selects the routines to execute basedon the instructions supported by the processor which is currentlyexecuting the code.

Exemplary Specific Vector Friendly Instruction Format

FIG. 29 is a block diagram illustrating an exemplary specific vectorfriendly instruction format according to embodiments of the invention.FIG. 29 shows a specific vector friendly instruction format 2900 that isspecific in the sense that it specifies the location, size,interpretation, and order of the fields, as well as values for some ofthose fields. The specific vector friendly instruction format 2900 maybe used to extend the x86 instruction set, and thus some of the fieldsare similar or the same as those used in the existing x86 instructionset and extension thereof (e.g., AVX). This format remains consistentwith the prefix encoding field, real opcode byte field, MOD RIM field,SIB field, displacement field, and immediate fields of the existing x86instruction set with extensions. The fields from FIG. 28 into which thefields from FIG. 29 map are illustrated.

It should be understood that, although embodiments of the invention aredescribed with reference to the specific vector friendly instructionformat 2900 in the context of the generic vector friendly instructionformat 2800 for illustrative purposes, the invention is not limited tothe specific vector friendly instruction format 2900 except whereclaimed. For example, the generic vector friendly instruction format2800 contemplates a variety of possible sizes for the various fields,while the specific vector friendly instruction format 2900 is shown ashaving fields of specific sizes. By way of specific example, while thedata element width field 2864 is illustrated as a one bit field in thespecific vector friendly instruction format 2900, the invention is notso limited (that is, the generic vector friendly instruction format 2800contemplates other sizes of the data element width field 2864).

The generic vector friendly instruction format 2800 includes thefollowing fields listed below in the order illustrated in FIG. 29A.

EVEX Prefix (Bytes 0-3) 2902—is encoded in a four-byte form.

Format Field 2840 (EVEX Byte 0, bits [7:0])—the first byte (EVEX Byte 0)is the format field 2840 and it contains 0x62 (the unique value used fordistinguishing the vector friendly instruction format in one embodimentof the invention).

The second-fourth bytes (EVEX Bytes 1-3) include a number of bit fieldsproviding specific capability.

REX field 2905 (EVEX Byte 1, bits [7-5])—consists of a EVEX.R bit field(EVEX Byte 1, bit [7]—R), EVEX.X bit field (EVEX byte 1, bit [6]—X), and2857BEX byte 1, bit[5]—B). The EVEX.R, EVEX.X, and EVEX.B bit fieldsprovide the same functionality as the corresponding VEX bit fields, andare encoded using 1s complement form, i.e. ZMM0 is encoded as 1111B,ZMM15 is encoded as 0000B. Other fields of the instructions encode thelower three bits of the register indexes as is known in the art (rrr,xxx, and bbb), so that Rrrr, Xxxx, and Bbbb may be formed by addingEVEX.R, EVEX.X, and EVEX.B.

REX′ field 2810—this is the first part of the REX′ field 2810 and is theEVEX.R′ bit field (EVEX Byte 1, bit [4]—R′) that is used to encodeeither the upper 16 or lower 16 of the extended 32 register set. In oneembodiment of the invention, this bit, along with others as indicatedbelow, is stored in bit inverted format to distinguish (in thewell-known x86 32-bit mode) from the BOUND instruction, whose realopcode byte is 62, but does not accept in the MOD R/M field (describedbelow) the value of 11 in the MOD field; alternative embodiments of theinvention do not store this and the other indicated bits below in theinverted format. A value of 1 is used to encode the lower 16 registers.In other words, R′Rrrr is formed by combining EVEX.R′, EVEX.R, and theother RRR from other fields.

Opcode map field 2915 (EVEX byte 1, bits [3:0]—mmmm)—its content encodesan implied leading opcode byte (0F, 0F 38, or 0F 3).

Data element width field 2864 (EVEX byte 2, bit [7]—W)—is represented bythe notation EVEX.W. EVEX.W is used to define the granularity (size) ofthe datatype (either 32-bit data elements or 64-bit data elements).

EVEX.vvvv 2920 (EVEX Byte 2, bits [6:3]—vvvv)—the role of EVEX.vvvv mayinclude the following: 1) EVEX.vvvv encodes the first source registeroperand, specified in inverted (1s complement) form and is valid forinstructions with 2 or more source operands; 2) EVEX.vvvv encodes thedestination register operand, specified in 1s complement form forcertain vector shifts; or 3) EVEX.vvvv does not encode any operand, thefield is reserved and should contain 1111b. Thus, EVEX.vvvv field 2920encodes the 4 low-order bits of the first source register specifierstored in inverted (1s complement) form. Depending on the instruction,an extra different EVEX bit field is used to extend the specifier sizeto 32 registers.

EVEX.U 2868 Class field (EVEX byte 2, bit [2]—U)—If EVEX.U=0, itindicates class A or EVEX.U0; if EVEX.U=1, it indicates class B orEVEX.U1.

Prefix encoding field 2925 (EVEX byte 2, bits [1:0]—pp)—providesadditional bits for the base operation field. In addition to providingsupport for the legacy SSE instructions in the EVEX prefix format, thisalso has the benefit of compacting the SIMD prefix (rather thanrequiring a byte to express the SIMD prefix, the EVEX prefix requiresonly 2 bits). In one embodiment, to support legacy SSE instructions thatuse a SIMD prefix (66H, F2H, F3H) in both the legacy format and in theEVEX prefix format, these legacy SIMD prefixes are encoded into the SIMDprefix encoding field; and at runtime are expanded into the legacy SIMDprefix prior to being provided to the decoder's PLA (so the PLA canexecute both the legacy and EVEX format of these legacy instructionswithout modification). Although newer instructions could use the EVEXprefix encoding field's content directly as an opcode extension, certainembodiments expand in a similar fashion for consistency but allow fordifferent meanings to be specified by these legacy SIMD prefixes. Analternative embodiment may redesign the PLA to support the 2 bit SIMDprefix encodings, and thus not require the expansion.

Alpha field 2852 (EVEX byte 3, bit [7]—EH; also known as EVEX.EH,EVEX.rs, EVEX.RL, EVEX.write mask control, and EVEX.N; also illustratedwith α)—as previously described, this field is context specific.

Beta field 2854 (EVEX byte 3, bits [6:4]—SSS, also known as EVEX.s₂₋₀,EVEX.r₂₋₀, EVEX.rr1, EVEX.LL0, EVEX.LLB; also illustrated with βββ)—aspreviously described, this field is context specific.

REX′ field 2810—this is the remainder of the REX′ field and is theEVEX.V′ bit field (EVEX Byte 3, bit [3]—V′) that may be used to encodeeither the upper 16 or lower 16 of the extended 32 register set. Thisbit is stored in bit inverted format. A value of 1 is used to encode thelower 16 registers. In other words, V′VVVV is formed by combiningEVEX.V′, EVEX.vvvv.

Write mask field 2870 (EVEX byte 3, bits [2:0]—kkk)—its contentspecifies the index of a register in the write mask registers aspreviously described. In one embodiment of the invention, the specificvalue EVEX.kkk=000 has a special behavior implying no write mask is usedfor the particular instruction (this may be implemented in a variety ofways including the use of a write mask hardwired to all ones or hardwarethat bypasses the masking hardware).

Real Opcode Field 2930 (Byte 4) is also known as the opcode byte. Partof the opcode is specified in this field.

MOD R/M Field 2940 (Byte 5) includes MOD field 2942, Reg field 2944, andR/M field 2946. As previously described, the MOD field's 2942 contentdistinguishes between memory access and non-memory access operations.The role of Reg field 2944 can be summarized to two situations: encodingeither the destination register operand or a source register operand, orbe treated as an opcode extension and not used to encode any instructionoperand. The role of R/M field 2946 may include the following: encodingthe instruction operand that references a memory address, or encodingeither the destination register operand or a source register operand.

Scale, Index, Base (SIB) Byte (Byte 6)—As previously described, thescale field's 2850 content is used for memory address generation.SIB.xxx 2954 and SIB.bbb 2956—the contents of these fields have beenpreviously referred to with regard to the register indexes Xxxx andBbbb.

Displacement field 2862A (Bytes 7-10)—when MOD field 2942 contains 10,bytes 7-10 are the displacement field 2862A, and it works the same asthe legacy 32-bit displacement (disp32) and works at byte granularity.

Displacement factor field 2862B (Byte 7)—when MOD field 2942 contains01, byte 7 is the displacement factor field 2862B. The location of thisfield is that same as that of the legacy x86 instruction set 8-bitdisplacement (disp8), which works at byte granularity. Since disp8 issign extended, it can only address between −128 and 127 bytes offsets;in terms of 64 byte cache lines, disp8 uses 8 bits that can be set toonly four really useful values −128, −64, 0, and 64; since a greaterrange is often needed, disp32 is used; however, disp32 requires 4 bytes.In contrast to disp8 and disp32, the displacement factor field 2862B isa reinterpretation of disp8; when using displacement factor field 2862B,the actual displacement is determined by the content of the displacementfactor field multiplied by the size of the memory operand access (N).This type of displacement is referred to as disp8*N. This reduces theaverage instruction length (a single byte of used for the displacementbut with a much greater range). Such compressed displacement is based onthe assumption that the effective displacement is multiple of thegranularity of the memory access, and hence, the redundant low-orderbits of the address offset do not need to be encoded. In other words,the displacement factor field 2862B substitutes the legacy x86instruction set 8-bit displacement. Thus, the displacement factor field2862B is encoded the same way as an x86 instruction set 8-bitdisplacement (so no changes in the ModRM/SIB encoding rules) with theonly exception that disp8 is overloaded to disp8*N. In other words,there are no changes in the encoding rules or encoding lengths but onlyin the interpretation of the displacement value by hardware (which needsto scale the displacement by the size of the memory operand to obtain abyte-wise address offset).

Immediate field 2872 operates as previously described.

Full Opcode Field

FIG. 29B is a block diagram illustrating the fields of the specificvector friendly instruction format 2900 that make up the full opcodefield 2874 according to one embodiment of the invention. Specifically,the full opcode field 2874 includes the format field 2840, the baseoperation field 2842, and the data element width (W) field 2864. Thebase operation field 2842 includes the prefix encoding field 2925, theopcode map field 2915, and the real opcode field 2930.

Register Index Field

FIG. 29C is a block diagram illustrating the fields of the specificvector friendly instruction format 2900 that make up the register indexfield 2844 according to one embodiment of the invention. Specifically,the register index field 2844 includes the REX field 2905, the REX′field 2910, the MODR/M.reg field 2944, the MODR/M.r/m field 2946, theVVVV field 2920, xxx field 2954, and the bbb field 2956.

Augmentation Operation Field

FIG. 29D is a block diagram illustrating the fields of the specificvector friendly instruction format 2900 that make up the augmentationoperation field 2850 according to one embodiment of the invention. Whenthe class (U) field 2868 contains 0, it signifies EVEX.U0 (class A2868A); when it contains 1, it signifies EVEX.U1 (class B 2868B). WhenU=0 and the MOD field 2942 contains 11 (signifying a no memory accessoperation), the alpha field 2852 (EVEX byte 3, bit [7]—EH) isinterpreted as the rs field 2852A. When the rs field 2852A contains a 1(round 2852A.1), the beta field 2854 (EVEX byte 3, bits [6:4]—SSS) isinterpreted as the round control field 2854A. The round control field2854A includes a one bit SAE field 2856 and a two bit round operationfield 2858. When the rs field 2852A contains a 0 (data transform2852A.2), the beta field 2854 (EVEX byte 3, bits [6:4]—SSS) isinterpreted as a three bit data transform field 2854B. When U=0 and theMOD field 2942 contains 00, 01, or 10 (signifying a memory accessoperation), the alpha field 2852 (EVEX byte 3, bit [7]—EH) isinterpreted as the eviction hint (EH) field 2852B and the beta field2854 (EVEX byte 3, bits [6:4]—SSS) is interpreted as a three bit datamanipulation field 2854C.

When U=1, the alpha field 2852 (EVEX byte 3, bit [7]—EH) is interpretedas the write mask control (Z) field 2852C. When U=1 and the MOD field2942 contains 11 (signifying a no memory access operation), part of thebeta field 2854 (EVEX byte 3, bit [4]—S₀) is interpreted as the RL field2857A; when it contains a 1 (round 2857A.1) the rest of the beta field2854 (EVEX byte 3, bit [6-5]—S₂₋₁) is interpreted as the round operationfield 2859A, while when the RL field 2857A contains a 0 (VSIZE 2857.A2)the rest of the beta field 2854 (EVEX byte 3, bit [6-5]—S₂₋₁) isinterpreted as the vector length field 2859B (EVEX byte 3, bit[6-5]—L₁₋₀). When U=1 and the MOD field 2942 contains 00, 01, or 10(signifying a memory access operation), the beta field 2854 (EVEX byte3, bits [6:4]—SSS) is interpreted as the vector length field 2859B (EVEXbyte 3, bit [6-5]—L₁₋₀) and the broadcast field 2857B (EVEX byte 3, bit[4]—B).

Exemplary Register Architecture

FIG. 30 is a block diagram of a register architecture 3000 according toone embodiment of the invention. In the embodiment illustrated, thereare 32 vector registers 3010 that are 512 bits wide; these registers arereferenced as zmm0 through zmm31. The lower order 256 bits of the lower16 zmm registers are overlaid on registers ymm0-16. The lower order 128bits of the lower 16 zmm registers (the lower order 128 bits of the ymmregisters) are overlaid on registers xmm0-15. The specific vectorfriendly instruction format 2900 operates on these overlaid registerfile as illustrated in the below tables.

Adjustable Vector Length Class Operations Registers InstructionTemplates A (FIG. 2810, 2815, zmm registers (the vector that do notinclude the 28A; 2825, 2830 length is 64 byte) vector length field U =0) 2859B B (FIG. 2812 zmm registers (the vector 28B; length is 64 byte)U = 1) Instruction templates B (FIG. 2817, 2827 zmm, ymm, or xmm that doinclude the 28B; registers (the vector vector length field U = 1) lengthis 64 byte, 2859B 32 byte, or 16 byte) depending on the vector lengthfield 2859B

In other words, the vector length field 2859B selects between a maximumlength and one or more other shorter lengths, where each such shorterlength is half the length of the preceding length; and instructionstemplates without the vector length field 2859B operate on the maximumvector length. Further, in one embodiment, the class B instructiontemplates of the specific vector friendly instruction format 2900operate on packed or scalar single/double-precision floating point dataand packed or scalar integer data. Scalar operations are operationsperformed on the lowest order data element position in an zmm/ymm/xmmregister; the higher order data element positions are either left thesame as they were prior to the instruction or zeroed depending on theembodiment.

Write mask registers 3015—in the embodiment illustrated, there are 8write mask registers (k0 through k7), each 64 bits in size. In analternate embodiment, the write mask registers 3015 are 16 bits in size.As previously described, in one embodiment of the invention, the vectormask register k0 cannot be used as a write mask; when the encoding thatwould normally indicate k0 is used for a write mask, it selects ahardwired write mask of 0xFFFF, effectively disabling write masking forthat instruction.

General-purpose registers 3025—in the embodiment illustrated, there aresixteen 64-bit general-purpose registers that are used along with theexisting x86 addressing modes to address memory operands. Theseregisters are referenced by the names RAX, RBX, RCX, RDX, RBP, RSI, RDI,RSP, and R8 through R15.

Scalar floating point stack register file (x87 stack) 3045, on which isaliased the MMX packed integer flat register file 3050—in the embodimentillustrated, the x87 stack is an eight-element stack used to performscalar floating-point operations on 32/64/80-bit floating point datausing the x87 instruction set extension; while the MMX registers areused to perform operations on 64-bit packed integer data, as well as tohold operands for some operations performed between the MMX and XMMregisters.

Alternative embodiments of the invention may use wider or narrowerregisters. Additionally, alternative embodiments of the invention mayuse more, less, or different register files and registers.

Exemplary Core Architectures, Processors, and Computer Architectures

Processor cores may be implemented in different ways, for differentpurposes, and in different processors. For instance, implementations ofsuch cores may include: 1) a general purpose in-order core intended forgeneral-purpose computing; 2) a high performance general purposeout-of-order core intended for general-purpose computing; 3) a specialpurpose core intended primarily for graphics and/or scientific(throughput) computing. Implementations of different processors mayinclude: 1) a CPU including one or more general purpose in-order coresintended for general-purpose computing and/or one or more generalpurpose out-of-order cores intended for general-purpose computing; and2) a coprocessor including one or more special purpose cores intendedprimarily for graphics and/or scientific (throughput). Such differentprocessors lead to different computer system architectures, which mayinclude: 1) the coprocessor on a separate chip from the CPU; 2) thecoprocessor on a separate die in the same package as a CPU; 3) thecoprocessor on the same die as a CPU (in which case, such a coprocessoris sometimes referred to as special purpose logic, such as integratedgraphics and/or scientific (throughput) logic, or as special purposecores); and 4) a system on a chip that may include on the same die thedescribed CPU (sometimes referred to as the application core(s) orapplication processor(s)), the above described coprocessor, andadditional functionality. Exemplary core architectures are describednext, followed by descriptions of exemplary processors and computerarchitectures.

Exemplary Core Architectures

In-Order and Out-of-Order Core Block Diagram

FIG. 31A is a block diagram illustrating both an exemplary in-orderpipeline and an exemplary register renaming, out-of-orderissue/execution pipeline according to embodiments of the invention. FIG.31B is a block diagram illustrating both an exemplary embodiment of anin-order architecture core and an exemplary register renaming,out-of-order issue/execution architecture core to be included in aprocessor according to embodiments of the invention. The solid linedboxes in FIGS. 31A-B illustrate the in-order pipeline and in-order core,while the optional addition of the dashed lined boxes illustrates theregister renaming, out-of-order issue/execution pipeline and core. Giventhat the in-order aspect is a subset of the out-of-order aspect, theout-of-order aspect will be described.

In FIG. 31A, a processor pipeline 3100 includes a fetch stage 3102, alength decode stage 3104, a decode stage 3106, an allocation stage 3108,a renaming stage 3110, a scheduling (also known as a dispatch or issue)stage 3112, a register read/memory read stage 3114, an execute stage3116, a write back/memory write stage 3118, an exception handling stage3122, and a commit stage 3124.

FIG. 31B shows processor core 3190 including a front end unit 3130coupled to an execution engine unit 3150, and both are coupled to amemory unit 3170. The core 3190 may be a reduced instruction setcomputing (RISC) core, a complex instruction set computing (CISC) core,a very long instruction word (VLIW) core, or a hybrid or alternativecore type. As yet another option, the core 3190 may be a special-purposecore, such as, for example, a network or communication core, compressionengine, coprocessor core, general purpose computing graphics processingunit (GPGPU) core, graphics core, or the like.

The front end unit 3130 includes a branch prediction unit 3132 coupledto an instruction cache unit 3134, which is coupled to an instructiontranslation lookaside buffer (TLB) 3136, which is coupled to aninstruction fetch unit 3138, which is coupled to a decode unit 3140. Thedecode unit 3140 (or decoder) may decode instructions, and generate asan output one or more micro-operations, micro-code entry points,microinstructions, other instructions, or other control signals, whichare decoded from, or which otherwise reflect, or are derived from, theoriginal instructions. The decode unit 3140 may be implemented usingvarious different mechanisms. Examples of suitable mechanisms include,but are not limited to, look-up tables, hardware implementations,programmable logic arrays (PLAs), microcode read only memories (ROMs),etc. In one embodiment, the core 3190 includes a microcode ROM or othermedium that stores microcode for certain macroinstructions (e.g., indecode unit 3140 or otherwise within the front end unit 3130). Thedecode unit 3140 is coupled to a rename/allocator unit 3152 in theexecution engine unit 3150.

The execution engine unit 3150 includes the rename/allocator unit 3152coupled to a retirement unit 3154 and a set of one or more schedulerunit(s) 3156. The scheduler unit(s) 3156 represents any number ofdifferent schedulers, including reservations stations, centralinstruction window, etc. The scheduler unit(s) 3156 is coupled to thephysical register file(s) unit(s) 3158. Each of the physical registerfile(s) units 3158 represents one or more physical register files,different ones of which store one or more different data types, such asscalar integer, scalar floating point, packed integer, packed floatingpoint, vector integer, vector floating point, status (e.g., aninstruction pointer that is the address of the next instruction to beexecuted), etc. In one embodiment, the physical register file(s) unit3158 comprises a vector registers unit, a write mask registers unit, anda scalar registers unit. These register units may provide architecturalvector registers, vector mask registers, and general purpose registers.The physical register file(s) unit(s) 3158 is overlapped by theretirement unit 3154 to illustrate various ways in which registerrenaming and out-of-order execution may be implemented (e.g., using areorder buffer(s) and a retirement register file(s); using a futurefile(s), a history buffer(s), and a retirement register file(s); using aregister maps and a pool of registers; etc.). The retirement unit 3154and the physical register file(s) unit(s) 3158 are coupled to theexecution cluster(s) 3160. The execution cluster(s) 3160 includes a setof one or more execution units 3162 and a set of one or more memoryaccess units 3164. The execution units 3162 may perform variousoperations (e.g., shifts, addition, subtraction, multiplication) and onvarious types of data (e.g., scalar floating point, packed integer,packed floating point, vector integer, vector floating point). Whilesome embodiments may include a number of execution units dedicated tospecific functions or sets of functions, other embodiments may includeonly one execution unit or multiple execution units that all perform allfunctions. The scheduler unit(s) 3156, physical register file(s) unit(s)3158, and execution cluster(s) 3160 are shown as being possibly pluralbecause certain embodiments create separate pipelines for certain typesof data/operations (e.g., a scalar integer pipeline, a scalar floatingpoint/packed integer/packed floating point/vector integer/vectorfloating point pipeline, and/or a memory access pipeline that each havetheir own scheduler unit, physical register file(s) unit, and/orexecution cluster—and in the case of a separate memory access pipeline,certain embodiments are implemented in which only the execution clusterof this pipeline has the memory access unit(s) 3164). It should also beunderstood that where separate pipelines are used, one or more of thesepipelines may be out-of-order issue/execution and the rest in-order.

The set of memory access units 3164 is coupled to the memory unit 3170,which includes a data TLB unit 3172 coupled to a data cache unit 3174coupled to a level 2 (L2) cache unit 3176. In one exemplary embodiment,the memory access units 3164 may include a load unit, a store addressunit, and a store data unit, each of which is coupled to the data TLBunit 3172 in the memory unit 3170. The instruction cache unit 3134 isfurther coupled to a level 2 (L2) cache unit 3176 in the memory unit3170. The L2 cache unit 3176 is coupled to one or more other levels ofcache and eventually to a main memory.

By way of example, the exemplary register renaming, out-of-orderissue/execution core architecture may implement the pipeline 3100 asfollows: 1) the instruction fetch 3138 performs the fetch and lengthdecoding stages 3102 and 3104; 2) the decode unit 3140 performs thedecode stage 3106; 3) the rename/allocator unit 3152 performs theallocation stage 3108 and renaming stage 3110; 4) the scheduler unit(s)3156 performs the schedule stage 3112; 5) the physical register file(s)unit(s) 3158 and the memory unit 3170 perform the register read/memoryread stage 3114; the execution cluster 3160 perform the execute stage3116; 6) the memory unit 3170 and the physical register file(s) unit(s)3158 perform the write back/memory write stage 3118; 7) various unitsmay be involved in the exception handling stage 3122; and 8) theretirement unit 3154 and the physical register file(s) unit(s) 3158perform the commit stage 3124.

The core 3190 may support one or more instructions sets (e.g., the x86instruction set (with some extensions that have been added with newerversions); the MIPS instruction set of MIPS Technologies of Sunnyvale,Calif.; the ARM instruction set (with optional additional extensionssuch as NEON) of ARM Holdings of Sunnyvale, Calif.), including theinstruction(s) described herein. In one embodiment, the core 3190includes logic to support a packed data instruction set extension (e.g.,AVX1, AVX2), thereby allowing the operations used by many multimediaapplications to be performed using packed data.

It should be understood that the core may support multithreading(executing two or more parallel sets of operations or threads), and maydo so in a variety of ways including time sliced multithreading,simultaneous multithreading (where a single physical core provides alogical core for each of the threads that physical core issimultaneously multithreading), or a combination thereof (e.g., timesliced fetching and decoding and simultaneous multithreading thereaftersuch as in the Intel® Hyperthreading technology).

While register renaming is described in the context of out-of-orderexecution, it should be understood that register renaming may be used inan in-order architecture. While the illustrated embodiment of theprocessor also includes separate instruction and data cache units3134/3174 and a shared L2 cache unit 3176, alternative embodiments mayhave a single internal cache for both instructions and data, such as,for example, a Level 1 (L1) internal cache, or multiple levels ofinternal cache. In some embodiments, the system may include acombination of an internal cache and an external cache that is externalto the core and/or the processor. Alternatively, all of the cache may beexternal to the core and/or the processor.

Specific Exemplary in-Order Core Architecture

FIGS. 32A-B illustrate a block diagram of a more specific exemplaryin-order core architecture, which core would be one of several logicblocks (including other cores of the same type and/or different types)in a chip. The logic blocks communicate through a high-bandwidthinterconnect network (e.g., a ring network) with some fixed functionlogic, memory I/O interfaces, and other necessary I/O logic, dependingon the application.

FIG. 32A is a block diagram of a single processor core, along with itsconnection to the on-die interconnect network 3202 and with its localsubset of the Level 2 (L2) cache 3204, according to embodiments of theinvention. In one embodiment, an instruction decoder 3200 supports thex86 instruction set with a packed data instruction set extension. An L1cache 3206 allows low-latency accesses to cache memory into the scalarand vector units. While in one embodiment (to simplify the design), ascalar unit 3208 and a vector unit 3210 use separate register sets(respectively, scalar registers 3212 and vector registers 3214) and datatransferred between them is written to memory and then read back in froma level 1 (L1) cache 3206, alternative embodiments of the invention mayuse a different approach (e.g., use a single register set or include acommunication path that allow data to be transferred between the tworegister files without being written and read back).

The local subset of the L2 cache 3204 is part of a global L2 cache thatis divided into separate local subsets, one per processor core. Eachprocessor core has a direct access path to its own local subset of theL2 cache 3204. Data read by a processor core is stored in its L2 cachesubset 3204 and can be accessed quickly, in parallel with otherprocessor cores accessing their own local L2 cache subsets. Data writtenby a processor core is stored in its own L2 cache subset 3204 and isflushed from other subsets, if necessary. The ring network ensurescoherency for shared data. The ring network is bi-directional to allowagents such as processor cores, L2 caches and other logic blocks tocommunicate with each other within the chip. Each ring data-path is1012-bits wide per direction.

FIG. 32B is an expanded view of part of the processor core in FIG. 32Aaccording to embodiments of the invention. FIG. 32B includes an L1 datacache 3206A part of the L1 cache 3204, as well as more detail regardingthe vector unit 3210 and the vector registers 3214. Specifically, thevector unit 3210 is a 16-wide vector processing unit (VPU) (see the16-wide ALU 3228), which executes one or more of integer,single-precision float, and double-precision float instructions. The VPUsupports swizzling the register inputs with swizzle unit 3220, numericconversion with numeric convert units 3222A-B, and replication withreplication unit 3224 on the memory input. Write mask registers 3226allow predicating resulting vector writes.

Processor with Integrated Memory Controller and Graphics

FIG. 33 is a block diagram of a processor 3300 that may have more thanone core, may have an integrated memory controller, and may haveintegrated graphics according to embodiments of the invention. The solidlined boxes in FIG. 33 illustrate a processor 3300 with a single core3302A, a system agent 3310, a set of one or more bus controller units3316, while the optional addition of the dashed lined boxes illustratesan alternative processor 3300 with multiple cores 3302A-N, a set of oneor more integrated memory controller unit(s) 3314 in the system agentunit 3310, and special purpose logic 3308.

Thus, different implementations of the processor 3300 may include: 1) aCPU with the special purpose logic 3308 being integrated graphics and/orscientific (throughput) logic (which may include one or more cores), andthe cores 3302A-N being one or more general purpose cores (e.g., generalpurpose in-order cores, general purpose out-of-order cores, acombination of the two); 2) a coprocessor with the cores 3302A-N being alarge number of special purpose cores intended primarily for graphicsand/or scientific (throughput); and 3) a coprocessor with the cores3302A-N being a large number of general purpose in-order cores. Thus,the processor 3300 may be a general-purpose processor, coprocessor orspecial-purpose processor, such as, for example, a network orcommunication processor, compression engine, graphics processor, GPGPU(general purpose graphics processing unit), a high-throughput manyintegrated core (MIC) coprocessor (including 30 or more cores), embeddedprocessor, or the like. The processor may be implemented on one or morechips. The processor 3300 may be a part of and/or may be implemented onone or more substrates using any of a number of process technologies,such as, for example, BiCMOS, CMOS, or NMOS.

The memory hierarchy includes one or more levels of cache within thecores, a set or one or more shared cache units 3306, and external memory(not shown) coupled to the set of integrated memory controller units3314. The set of shared cache units 3306 may include one or moremid-level caches, such as level 2 (L2), level 3 (L3), level 4 (L4), orother levels of cache, a last level cache (LLC), and/or combinationsthereof. While in one embodiment a ring based interconnect unit 3312interconnects the integrated graphics logic 3308, the set of sharedcache units 3306, and the system agent unit 3310/integrated memorycontroller unit(s) 3314, alternative embodiments may use any number ofwell-known techniques for interconnecting such units. In one embodiment,coherency is maintained between one or more cache units 3306 and cores3302-A-N.

In some embodiments, one or more of the cores 3302A-N are capable ofmulti-threading. The system agent 3310 includes those componentscoordinating and operating cores 3302A-N. The system agent unit 3310 mayinclude for example a power control unit (PCU) and a display unit. ThePCU may be or include logic and components needed for regulating thepower state of the cores 3302A-N and the integrated graphics logic 3308.The display unit is for driving one or more externally connecteddisplays.

The cores 3302A-N may be homogenous or heterogeneous in terms ofarchitecture instruction set; that is, two or more of the cores 3302A-Nmay be capable of execution the same instruction set, while others maybe capable of executing only a subset of that instruction set or adifferent instruction set.

Exemplary Computer Architectures

FIGS. 34-37 are block diagrams of exemplary computer architectures.Other system designs and configurations known in the arts for laptops,desktops, handheld PCs, personal digital assistants, engineeringworkstations, servers, network devices, network hubs, switches, embeddedprocessors, digital signal processors (DSPs), graphics devices, videogame devices, set-top boxes, micro controllers, cell phones, portablemedia players, hand held devices, and various other electronic devices,are also suitable. In general, a huge variety of systems or electronicdevices capable of incorporating a processor and/or other executionlogic as disclosed herein are generally suitable.

Referring now to FIG. 34, shown is a block diagram of a system 3400 inaccordance with one embodiment of the present invention. The system 3400may include one or more processors 3410, 3415, which are coupled to acontroller hub 3420. In one embodiment the controller hub 3420 includesa graphics memory controller hub (GMCH) 3490 and an Input/Output Hub(IOH) 3450 (which may be on separate chips); the GMCH 3490 includesmemory and graphics controllers to which are coupled memory 3440 and acoprocessor 3445; the IOH 3450 is couples input/output (I/O) devices3460 to the GMCH 3490. Alternatively, one or both of the memory andgraphics controllers are integrated within the processor (as describedherein), the memory 3440 and the coprocessor 3445 are coupled directlyto the processor 3410, and the controller hub 3420 in a single chip withthe IOH 3450.

The optional nature of additional processors 3415 is denoted in FIG. 34with broken lines. Each processor 3410, 3415 may include one or more ofthe processing cores described herein and may be some version of theprocessor 3300.

The memory 3440 may be, for example, dynamic random access memory(DRAM), phase change memory (PCM), or a combination of the two. For atleast one embodiment, the controller hub 3420 communicates with theprocessor(s) 3410, 3415 via a multi-drop bus, such as a frontside bus(FSB), point-to-point interface such as QuickPath Interconnect (QPI), orsimilar connection 3495.

In one embodiment, the coprocessor 3445 is a special-purpose processor,such as, for example, a high-throughput MIC processor, a network orcommunication processor, compression engine, graphics processor, GPGPU,embedded processor, or the like. In one embodiment, controller hub 3420may include an integrated graphics accelerator.

There can be a variety of differences between the physical resources3410, 3415 in terms of a spectrum of metrics of merit includingarchitectural, microarchitectural, thermal, power consumptioncharacteristics, and the like.

In one embodiment, the processor 3410 executes instructions that controldata processing operations of a general type. Embedded within theinstructions may be coprocessor instructions. The processor 3410recognizes these coprocessor instructions as being of a type that shouldbe executed by the attached coprocessor 3445. Accordingly, the processor3410 issues these coprocessor instructions (or control signalsrepresenting coprocessor instructions) on a coprocessor bus or otherinterconnect, to coprocessor 3445. Coprocessor(s) 3445 accept andexecute the received coprocessor instructions.

Referring now to FIG. 35, shown is a block diagram of a first morespecific exemplary system 3500 in accordance with an embodiment of thepresent invention. As shown in FIG. 35, multiprocessor system 3500 is apoint-to-point interconnect system, and includes a first processor 3570and a second processor 3580 coupled via a point-to-point interconnect3550. Each of processors 3570 and 3580 may be some version of theprocessor 3300. In one embodiment of the invention, processors 3570 and3580 are respectively processors 3410 and 3415, while coprocessor 3538is coprocessor 3445. In another embodiment, processors 3570 and 3580 arerespectively processor 3410 coprocessor 3445.

Processors 3570 and 3580 are shown including integrated memorycontroller (IMC) units 3572 and 3582, respectively. Processor 3570 alsoincludes as part of its bus controller units point-to-point (P-P)interfaces 3576 and 3578; similarly, second processor 3580 includes P-Pinterfaces 3586 and 3588. Processors 3570, 3580 may exchange informationvia a point-to-point (P-P) interface 3550 using P-P interface circuits3578, 3588. As shown in FIG. 35, IMCs 3572 and 3582 couple theprocessors to respective memories, namely a memory 3532 and a memory3534, which may be portions of main memory locally attached to therespective processors.

Processors 3570, 3580 may each exchange information with a chipset 3590via individual P-P interfaces 3552, 3554 using point to point interfacecircuits 3576, 3594, 3586, 3598. Chipset 3590 may optionally exchangeinformation with the coprocessor 3538 via a high-performance interface3539. In one embodiment, the coprocessor 3538 is a special-purposeprocessor, such as, for example, a high-throughput MIC processor, anetwork or communication processor, compression engine, graphicsprocessor, GPGPU, embedded processor, or the like.

A shared cache (not shown) may be included in either processor oroutside of both processors, yet connected with the processors via P-Pinterconnect, such that either or both processors' local cacheinformation may be stored in the shared cache if a processor is placedinto a low power mode.

Chipset 3590 may be coupled to a first bus 3516 via an interface 3596.In one embodiment, first bus 3516 may be a Peripheral ComponentInterconnect (PCI) bus, or a bus such as a PCI Express bus or anotherthird generation I/O interconnect bus, although the scope of the presentinvention is not so limited.

As shown in FIG. 35, various I/O devices 3514 may be coupled to firstbus 3516, along with a bus bridge 3518 which couples first bus 3516 to asecond bus 3520. In one embodiment, one or more additional processor(s)3515, such as coprocessors, high-throughput MIC processors, GPGPU's,accelerators (such as, e.g., graphics accelerators or digital signalprocessing (DSP) units), field programmable gate arrays, or any otherprocessor, are coupled to first bus 3516. In one embodiment, second bus3520 may be a low pin count (LPC) bus. Various devices may be coupled toa second bus 3520 including, for example, a keyboard and/or mouse 3522,communication devices 3527 and a storage unit 3528 such as a disk driveor other mass storage device which may include instructions/code anddata 3530, in one embodiment. Further, an audio I/O 3524 may be coupledto the second bus 3520. Note that other architectures are possible. Forexample, instead of the point-to-point architecture of FIG. 35, a systemmay implement a multi-drop bus or other such architecture.

Referring now to FIG. 36, shown is a block diagram of a second morespecific exemplary system 3600 in accordance with an embodiment of thepresent invention. Like elements in FIGS. 35 and 36 bear like referencenumerals, and certain aspects of FIG. 35 have been omitted from FIG. 36in order to avoid obscuring other aspects of FIG. 36.

FIG. 36 illustrates that the processors 3570, 3580 may includeintegrated memory and I/O control logic (“CL”) 3572 and 3582,respectively. Thus, the CL 3572, 3582 include integrated memorycontroller units and include I/O control logic. FIG. 36 illustrates thatnot only are the memories 3532, 3534 coupled to the CL 3572, 3582, butalso that I/O devices 3614 are also coupled to the control logic 3572,3582. Legacy I/O devices 3615 are coupled to the chipset 3590.

Referring now to FIG. 37, shown is a block diagram of a SoC 3700 inaccordance with an embodiment of the present invention. Similar elementsin FIG. 33 bear like reference numerals. Also, dashed lined boxes areoptional features on more advanced SoCs. In FIG. 37, an interconnectunit(s) 3702 is coupled to: an application processor 3710 which includesa set of one or more cores 202A-N and shared cache unit(s) 3306; asystem agent unit 3310; a bus controller unit(s) 3316; an integratedmemory controller unit(s) 3314; a set or one or more coprocessors 3720which may include integrated graphics logic, an image processor, anaudio processor, and a video processor; an static random access memory(SRAM) unit 3730; a direct memory access (DMA) unit 3732; and a displayunit 3740 for coupling to one or more external displays. In oneembodiment, the coprocessor(s) 3720 include a special-purpose processor,such as, for example, a network or communication processor, compressionengine, GPGPU, a high-throughput MIC processor, embedded processor, orthe like.

Embodiments of the mechanisms disclosed herein may be implemented inhardware, software, firmware, or a combination of such implementationapproaches. Embodiments of the invention may be implemented as computerprograms or program code executing on programmable systems comprising atleast one processor, a storage system (including volatile andnon-volatile memory and/or storage elements), at least one input device,and at least one output device.

Program code, such as code 3530 illustrated in FIG. 35, may be appliedto input instructions to perform the functions described herein andgenerate output information. The output information may be applied toone or more output devices, in known fashion. For purposes of thisapplication, a processing system includes any system that has aprocessor, such as, for example; a digital signal processor (DSP), amicrocontroller, an application specific integrated circuit (ASIC), or amicroprocessor.

The program code may be implemented in a high level procedural or objectoriented programming language to communicate with a processing system.The program code may also be implemented in assembly or machinelanguage, if desired. In fact, the mechanisms described herein are notlimited in scope to any particular programming language. In any case,the language may be a compiled or interpreted language.

One or more aspects of at least one embodiment may be implemented byrepresentative instructions stored on a machine-readable medium whichrepresents various logic within the processor, which when read by amachine causes the machine to fabricate logic to perform the techniquesdescribed herein. Such representations, known as “IP cores” may bestored on a tangible, machine readable medium and supplied to variouscustomers or manufacturing facilities to load into the fabricationmachines that actually make the logic or processor.

Such machine-readable storage media may include, without limitation,non-transitory, tangible arrangements of articles manufactured or formedby a machine or device, including storage media such as hard disks, anyother type of disk including floppy disks, optical disks, compact diskread-only memories (CD-ROMs), compact disk rewritable's (CD-RWs), andmagneto-optical disks, semiconductor devices such as read-only memories(ROMs), random access memories (RAMs) such as dynamic random accessmemories (DRAMs), static random access memories (SRAMs), erasableprogrammable read-only memories (EPROMs), flash memories, electricallyerasable programmable read-only memories (EEPROMs), phase change memory(PCM), magnetic or optical cards, or any other type of media suitablefor storing electronic instructions.

Accordingly, embodiments of the invention also include non-transitory,tangible machine-readable media containing instructions or containingdesign data, such as Hardware Description Language (HDL), which definesstructures, circuits, apparatuses, processors and/or system featuresdescribed herein. Such embodiments may also be referred to as programproducts.

Emulation (including binary translation, code morphing, etc.)

In some cases, an instruction converter may be used to convert aninstruction from a source instruction set to a target instruction set.For example, the instruction converter may translate (e.g., using staticbinary translation, dynamic binary translation including dynamiccompilation), morph, emulate, or otherwise convert an instruction to oneor more other instructions to be processed by the core. The instructionconverter may be implemented in software, hardware, firmware, or acombination thereof. The instruction converter may be on processor, offprocessor, or part on and part off processor.

FIG. 38 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention. In the illustrated embodiment, the instructionconverter is a software instruction converter, although alternativelythe instruction converter may be implemented in software, firmware,hardware, or various combinations thereof. FIG. 38 shows a program in ahigh level language 3802 may be compiled using an x86 compiler 3804 togenerate x86 binary code 3806 that may be natively executed by aprocessor with at least one x86 instruction set core 3816. The processorwith at least one x86 instruction set core 3816 represents any processorthat can perform substantially the same functions as an Intel processorwith at least one x86 instruction set core by compatibly executing orotherwise processing (1) a substantial portion of the instruction set ofthe Intel x86 instruction set core or (2) object code versions ofapplications or other software targeted to run on an Intel processorwith at least one x86 instruction set core, in order to achievesubstantially the same result as an Intel processor with at least onex86 instruction set core. The x86 compiler 3804 represents a compilerthat is operable to generate x86 binary code 3806 (e.g., object code)that can, with or without additional linkage processing, be executed onthe processor with at least one x86 instruction set core 3816.Similarly, FIG. 38 shows the program in the high level language 3802 maybe compiled using an alternative instruction set compiler 3808 togenerate alternative instruction set binary code 3810 that may benatively executed by a processor without at least one x86 instructionset core 3814 (e.g., a processor with cores that execute the MIPSinstruction set of MIPS Technologies of Sunnyvale, Calif. and/or thatexecute the ARM instruction set of ARM Holdings of Sunnyvale, Calif.).The instruction converter 3812 is used to convert the x86 binary code3806 into code that may be natively executed by the processor without anx86 instruction set core 3814. This converted code is not likely to bethe same as the alternative instruction set binary code 3810 because aninstruction converter capable of this is difficult to make; however, theconverted code will accomplish the general operation and be made up ofinstructions from the alternative instruction set. Thus, the instructionconverter 3812 represents software, firmware, hardware, or a combinationthereof that, through emulation, simulation or any other process, allowsa processor or other electronic device that does not have an x86instruction set processor or core to execute the x86 binary code 3806.

We claim:
 1. An apparatus comprising: a hardware decoder to decode aninstruction, the instruction to include an opcode and an operand tostore a portion of a fallback address; and execution hardware to executethe decoded instruction to initiate a data speculative execution (DSX)region by activating DSX tracking hardware to track speculative memoryaccesses and detect ordering violations in the DSX region, and storingthe fallback address.
 2. The apparatus of claim 1, wherein the portionof the fallback address is a displacement value to be added to aninstruction pointer of an instruction immediately following the decodedinstruction by the execution hardware.
 3. The apparatus of claim 1,wherein the portion of the fallback address is a complete address. 4.The apparatus of claim 1, wherein the operand to store a portion of thefallback address is an immediate value.
 5. The apparatus of claim 1,wherein the operand to store a portion of the fallback address is aregister.
 6. The apparatus of claim 1, wherein the execution hardware tofurther to determine that an restricted transactional memory (RTM)transaction is occurring and process the RTM transaction.
 7. Theapparatus of claim 1, further comprising: a DSX nesting counter to storea value corresponding to a number of DSX region starts with nocorresponding DSX region ends.
 8. An method comprising: decoding aninstruction using a hardware decoder, the instruction to include anopcode and an operand to store a portion of a fallback address; andexecuting decoded instruction to initiate a data speculative execution(DSX) region by activating DSX tracking hardware to track speculativememory accesses and detect ordering violations in the DSX region, andstoring the fallback address.
 9. The method of claim 8, wherein theportion of the fallback address is a displacement value to be added toan instruction pointer of an instruction immediately following thedecoded instruction by the execution hardware.
 10. The method of claim8, wherein the portion of the fallback address is a complete address.11. The method of claim 8, wherein the operand to store a portion of thefallback address is an immediate value.
 12. The method of claim 8,wherein the operand to store a portion of the fallback address is aregister.
 13. The method of claim 8, wherein the executing furthercomprise: determining that an restricted transactional memory (RTM)transaction is occurring and process the RTM transaction.
 14. The methodof claim 8, further comprising: storing a value corresponding to anumber of DSX region starts with no corresponding DSX region ends.
 15. Anon-transitory machine readable medium storing instructions which whenexecuted by a machine cause circuitry to be fabricated, the circuitrycomprising: a hardware decoder to decode an instruction, the instructionto include an opcode and an operand to store a portion of a fallbackaddress; and execution hardware to execute the decoded instruction toinitiate a data speculative execution (DSX) region by activating DSXtracking hardware to track speculative memory accesses and detectordering violations in the DSX region, and storing the fallback address.16. The non-transitory machine readable medium of claim 15, wherein theportion of the fallback address is a displacement value to be added toan instruction pointer of an instruction immediately following thedecoded instruction by the execution hardware.
 17. The non-transitorymachine readable medium of claim 15, wherein the portion of the fallbackaddress is a complete address.
 18. The non-transitory machine readablemedium of claim 15, wherein the operand to store a portion of thefallback address is an immediate value.